34b7db3bbc
Features/docs
547 lines
18 KiB
Rust
547 lines
18 KiB
Rust
//! Support for fmt! expressions.
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//!
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//! The syntax is close to that of Posix format strings:
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//!
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//! ~~~~~~
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//! Format := '%' Parameter? Flag* Width? Precision? Type
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//! Parameter := [0-9]+ '$'
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//! Flag := [ 0#+-]
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//! Width := Parameter | [0-9]+
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//! Precision := '.' [0-9]+
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//! Type := [bcdfiostuxX?]
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//! ~~~~~~
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//!
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//! * Parameter is the 1-based argument to apply the format to. Currently not
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//! implemented.
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//! * Flag 0 causes leading zeros to be used for padding when converting
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//! numbers.
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//! * Flag # causes the conversion to be done in an *alternative* manner.
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//! Currently not implemented.
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//! * Flag + causes signed numbers to always be prepended with a sign
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//! character.
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//! * Flag - left justifies the result
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//! * Width specifies the minimum field width of the result. By default
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//! leading spaces are added.
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//! * Precision specifies the minimum number of digits for integral types
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//! and the minimum number
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//! of decimal places for float.
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//!
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//! The types currently supported are:
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//!
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//! * b - bool
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//! * c - char
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//! * d - int
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//! * f - float
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//! * i - int (same as d)
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//! * o - uint as octal
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//! * t - uint as binary
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//! * u - uint
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//! * x - uint as lower-case hexadecimal
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//! * X - uint as upper-case hexadecimal
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//! * s - str (any flavor)
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//! * ? - arbitrary type (does not use the to_str trait)
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// NB: transitionary, de-mode-ing.
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#[forbid(deprecated_mode)];
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#[forbid(deprecated_pattern)];
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/*
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Syntax Extension: fmt
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Format a string
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The 'fmt' extension is modeled on the posix printf system.
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A posix conversion ostensibly looks like this
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> %~[parameter]~[flags]~[width]~[.precision]~[length]type
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Given the different numeric type bestiary we have, we omit the 'length'
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parameter and support slightly different conversions for 'type'
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> %~[parameter]~[flags]~[width]~[.precision]type
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we also only support translating-to-rust a tiny subset of the possible
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combinations at the moment.
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Example:
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debug!("hello, %s!", "world");
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*/
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use cmp::Eq;
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use option::{Some, None};
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/*
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* We have a 'ct' (compile-time) module that parses format strings into a
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* sequence of conversions. From those conversions AST fragments are built
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* that call into properly-typed functions in the 'rt' (run-time) module.
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* Each of those run-time conversion functions accepts another conversion
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* description that specifies how to format its output.
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*
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* The building of the AST is currently done in a module inside the compiler,
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* but should migrate over here as the plugin interface is defined.
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*/
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// Functions used by the fmt extension at compile time
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#[doc(hidden)]
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pub mod ct {
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pub enum Signedness { Signed, Unsigned, }
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pub enum Caseness { CaseUpper, CaseLower, }
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pub enum Ty {
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TyBool,
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TyStr,
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TyChar,
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TyInt(Signedness),
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TyBits,
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TyHex(Caseness),
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TyOctal,
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TyFloat,
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TyPoly,
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}
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pub enum Flag {
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FlagLeftJustify,
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FlagLeftZeroPad,
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FlagSpaceForSign,
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FlagSignAlways,
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FlagAlternate,
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}
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pub enum Count {
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CountIs(uint),
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CountIsParam(uint),
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CountIsNextParam,
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CountImplied,
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}
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// A formatted conversion from an expression to a string
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pub type Conv =
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{param: Option<uint>,
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flags: ~[Flag],
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width: Count,
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precision: Count,
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ty: Ty};
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// A fragment of the output sequence
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pub enum Piece { PieceString(~str), PieceConv(Conv), }
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pub type ErrorFn = fn@(&str) -> ! ;
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pub fn parse_fmt_string(s: &str, err: ErrorFn) -> ~[Piece] {
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let mut pieces: ~[Piece] = ~[];
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let lim = str::len(s);
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let mut buf = ~"";
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fn flush_buf(buf: ~str, pieces: &mut ~[Piece]) -> ~str {
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if buf.len() > 0 {
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let piece = PieceString(move buf);
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pieces.push(move piece);
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}
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return ~"";
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}
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let mut i = 0;
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while i < lim {
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let size = str::utf8_char_width(s[i]);
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let curr = str::slice(s, i, i+size);
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if curr == ~"%" {
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i += 1;
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if i >= lim {
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err(~"unterminated conversion at end of string");
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}
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let curr2 = str::slice(s, i, i+1);
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if curr2 == ~"%" {
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buf += curr2;
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i += 1;
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} else {
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buf = flush_buf(move buf, &mut pieces);
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let rs = parse_conversion(s, i, lim, err);
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pieces.push(copy rs.piece);
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i = rs.next;
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}
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} else { buf += curr; i += size; }
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}
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flush_buf(move buf, &mut pieces);
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move pieces
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}
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pub fn peek_num(s: &str, i: uint, lim: uint) ->
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Option<{num: uint, next: uint}> {
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let mut j = i;
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let mut accum = 0u;
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let mut found = false;
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while j < lim {
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match char::to_digit(s[j] as char, 10) {
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Some(x) => {
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found = true;
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accum *= 10;
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accum += x;
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j += 1;
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},
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None => break
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}
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}
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if found {
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Some({num: accum, next: j})
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} else {
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None
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}
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}
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pub fn parse_conversion(s: &str, i: uint, lim: uint,
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err: ErrorFn) ->
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{piece: Piece, next: uint} {
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let parm = parse_parameter(s, i, lim);
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let flags = parse_flags(s, parm.next, lim);
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let width = parse_count(s, flags.next, lim);
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let prec = parse_precision(s, width.next, lim);
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let ty = parse_type(s, prec.next, lim, err);
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return {piece:
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PieceConv({param: parm.param,
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flags: copy flags.flags,
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width: width.count,
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precision: prec.count,
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ty: ty.ty}),
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next: ty.next};
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}
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pub fn parse_parameter(s: &str, i: uint, lim: uint) ->
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{param: Option<uint>, next: uint} {
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if i >= lim { return {param: None, next: i}; }
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let num = peek_num(s, i, lim);
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return match num {
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None => {param: None, next: i},
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Some(t) => {
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let n = t.num;
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let j = t.next;
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if j < lim && s[j] == '$' as u8 {
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{param: Some(n), next: j + 1}
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} else { {param: None, next: i} }
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}
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};
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}
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pub fn parse_flags(s: &str, i: uint, lim: uint) ->
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{flags: ~[Flag], next: uint} {
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let noflags: ~[Flag] = ~[];
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if i >= lim { return {flags: move noflags, next: i}; }
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fn more(f: Flag, s: &str, i: uint, lim: uint) ->
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{flags: ~[Flag], next: uint} {
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let next = parse_flags(s, i + 1u, lim);
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let rest = copy next.flags;
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let j = next.next;
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let curr: ~[Flag] = ~[f];
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return {flags: vec::append(move curr, rest), next: j};
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}
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// Unfortunate, but because s is borrowed, can't use a closure
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// fn more(f: Flag, s: &str) { more_(f, s, i, lim); }
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let f = s[i];
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return if f == '-' as u8 {
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more(FlagLeftJustify, s, i, lim)
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} else if f == '0' as u8 {
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more(FlagLeftZeroPad, s, i, lim)
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} else if f == ' ' as u8 {
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more(FlagSpaceForSign, s, i, lim)
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} else if f == '+' as u8 {
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more(FlagSignAlways, s, i, lim)
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} else if f == '#' as u8 {
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more(FlagAlternate, s, i, lim)
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} else { {flags: move noflags, next: i} };
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}
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pub fn parse_count(s: &str, i: uint, lim: uint)
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-> {count: Count, next: uint} {
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return if i >= lim {
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{count: CountImplied, next: i}
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} else if s[i] == '*' as u8 {
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let param = parse_parameter(s, i + 1, lim);
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let j = param.next;
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match param.param {
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None => {count: CountIsNextParam, next: j},
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Some(n) => {count: CountIsParam(n), next: j}
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}
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} else {
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let num = peek_num(s, i, lim);
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match num {
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None => {count: CountImplied, next: i},
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Some(num) => {
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count: CountIs(num.num),
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next: num.next
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}
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}
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};
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}
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pub fn parse_precision(s: &str, i: uint, lim: uint) ->
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{count: Count, next: uint} {
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return if i >= lim {
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{count: CountImplied, next: i}
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} else if s[i] == '.' as u8 {
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let count = parse_count(s, i + 1u, lim);
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// If there were no digits specified, i.e. the precision
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// was ".", then the precision is 0
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match count.count {
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CountImplied => {count: CountIs(0), next: count.next},
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_ => count
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}
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} else { {count: CountImplied, next: i} };
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}
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pub fn parse_type(s: &str, i: uint, lim: uint, err: ErrorFn) ->
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{ty: Ty, next: uint} {
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if i >= lim { err(~"missing type in conversion"); }
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let tstr = str::slice(s, i, i+1u);
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// FIXME (#2249): Do we really want two signed types here?
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// How important is it to be printf compatible?
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let t =
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if tstr == ~"b" {
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TyBool
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} else if tstr == ~"s" {
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TyStr
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} else if tstr == ~"c" {
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TyChar
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} else if tstr == ~"d" || tstr == ~"i" {
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TyInt(Signed)
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} else if tstr == ~"u" {
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TyInt(Unsigned)
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} else if tstr == ~"x" {
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TyHex(CaseLower)
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} else if tstr == ~"X" {
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TyHex(CaseUpper)
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} else if tstr == ~"t" {
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TyBits
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} else if tstr == ~"o" {
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TyOctal
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} else if tstr == ~"f" {
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TyFloat
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} else if tstr == ~"?" {
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TyPoly
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} else { err(~"unknown type in conversion: " + tstr) };
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return {ty: t, next: i + 1u};
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}
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}
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// Functions used by the fmt extension at runtime. For now there are a lot of
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// decisions made a runtime. If it proves worthwhile then some of these
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// conditions can be evaluated at compile-time. For now though it's cleaner to
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// implement it 0this way, I think.
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#[doc(hidden)]
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pub mod rt {
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pub const flag_none : u32 = 0u32;
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pub const flag_left_justify : u32 = 0b00000000000001u32;
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pub const flag_left_zero_pad : u32 = 0b00000000000010u32;
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pub const flag_space_for_sign : u32 = 0b00000000000100u32;
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pub const flag_sign_always : u32 = 0b00000000001000u32;
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pub const flag_alternate : u32 = 0b00000000010000u32;
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pub enum Count { CountIs(uint), CountImplied, }
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pub enum Ty { TyDefault, TyBits, TyHexUpper, TyHexLower, TyOctal, }
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pub type Conv = {flags: u32, width: Count, precision: Count, ty: Ty};
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pub pure fn conv_int(cv: Conv, i: int) -> ~str {
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let radix = 10;
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let prec = get_int_precision(cv);
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let mut s : ~str = int_to_str_prec(i, radix, prec);
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if 0 <= i {
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if have_flag(cv.flags, flag_sign_always) {
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unsafe { str::unshift_char(&mut s, '+') };
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} else if have_flag(cv.flags, flag_space_for_sign) {
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unsafe { str::unshift_char(&mut s, ' ') };
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}
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}
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return unsafe { pad(cv, move s, PadSigned) };
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}
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pub pure fn conv_uint(cv: Conv, u: uint) -> ~str {
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let prec = get_int_precision(cv);
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let mut rs =
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match cv.ty {
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TyDefault => uint_to_str_prec(u, 10, prec),
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TyHexLower => uint_to_str_prec(u, 16, prec),
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TyHexUpper => str::to_upper(uint_to_str_prec(u, 16, prec)),
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TyBits => uint_to_str_prec(u, 2, prec),
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TyOctal => uint_to_str_prec(u, 8, prec)
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};
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return unsafe { pad(cv, move rs, PadUnsigned) };
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}
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pub pure fn conv_bool(cv: Conv, b: bool) -> ~str {
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let s = if b { ~"true" } else { ~"false" };
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// run the boolean conversion through the string conversion logic,
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// giving it the same rules for precision, etc.
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return conv_str(cv, s);
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}
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pub pure fn conv_char(cv: Conv, c: char) -> ~str {
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let mut s = str::from_char(c);
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return unsafe { pad(cv, move s, PadNozero) };
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}
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pub pure fn conv_str(cv: Conv, s: &str) -> ~str {
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// For strings, precision is the maximum characters
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// displayed
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let mut unpadded = match cv.precision {
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CountImplied => s.to_owned(),
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CountIs(max) => if max as uint < str::char_len(s) {
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str::substr(s, 0, max as uint)
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} else {
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s.to_owned()
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}
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};
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return unsafe { pad(cv, move unpadded, PadNozero) };
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}
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pub pure fn conv_float(cv: Conv, f: float) -> ~str {
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let (to_str, digits) = match cv.precision {
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CountIs(c) => (float::to_str_exact, c as uint),
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CountImplied => (float::to_str, 6u)
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};
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let mut s = unsafe { to_str(f, digits) };
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if 0.0 <= f {
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if have_flag(cv.flags, flag_sign_always) {
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s = ~"+" + s;
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} else if have_flag(cv.flags, flag_space_for_sign) {
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s = ~" " + s;
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}
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}
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return unsafe { pad(cv, move s, PadFloat) };
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}
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pub pure fn conv_poly<T>(cv: Conv, v: &T) -> ~str {
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let s = sys::log_str(v);
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return conv_str(cv, s);
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}
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// Convert an int to string with minimum number of digits. If precision is
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// 0 and num is 0 then the result is the empty string.
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pub pure fn int_to_str_prec(num: int, radix: uint, prec: uint) -> ~str {
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return if num < 0 {
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~"-" + uint_to_str_prec(-num as uint, radix, prec)
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} else { uint_to_str_prec(num as uint, radix, prec) };
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}
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// Convert a uint to string with a minimum number of digits. If precision
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// is 0 and num is 0 then the result is the empty string. Could move this
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// to uint: but it doesn't seem all that useful.
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pub pure fn uint_to_str_prec(num: uint, radix: uint,
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prec: uint) -> ~str {
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return if prec == 0u && num == 0u {
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~""
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} else {
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let s = uint::to_str(num, radix);
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let len = str::char_len(s);
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if len < prec {
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let diff = prec - len;
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let pad = str::from_chars(vec::from_elem(diff, '0'));
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pad + s
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} else { move s }
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};
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}
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pub pure fn get_int_precision(cv: Conv) -> uint {
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return match cv.precision {
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CountIs(c) => c as uint,
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CountImplied => 1u
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};
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}
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pub enum PadMode { PadSigned, PadUnsigned, PadNozero, PadFloat }
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pub impl PadMode : Eq {
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#[cfg(stage0)]
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pure fn eq(other: &PadMode) -> bool {
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match (self, (*other)) {
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(PadSigned, PadSigned) => true,
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(PadUnsigned, PadUnsigned) => true,
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(PadNozero, PadNozero) => true,
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(PadFloat, PadFloat) => true,
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(PadSigned, _) => false,
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(PadUnsigned, _) => false,
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(PadNozero, _) => false,
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(PadFloat, _) => false
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}
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}
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#[cfg(stage1)]
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#[cfg(stage2)]
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pure fn eq(&self, other: &PadMode) -> bool {
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match ((*self), (*other)) {
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(PadSigned, PadSigned) => true,
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(PadUnsigned, PadUnsigned) => true,
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(PadNozero, PadNozero) => true,
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(PadFloat, PadFloat) => true,
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(PadSigned, _) => false,
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(PadUnsigned, _) => false,
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(PadNozero, _) => false,
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(PadFloat, _) => false
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}
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}
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#[cfg(stage0)]
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pure fn ne(other: &PadMode) -> bool { !self.eq(other) }
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#[cfg(stage1)]
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#[cfg(stage2)]
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pure fn ne(&self, other: &PadMode) -> bool { !(*self).eq(other) }
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}
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pub fn pad(cv: Conv, s: ~str, mode: PadMode) -> ~str {
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let mut s = move s; // sadtimes
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let uwidth : uint = match cv.width {
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CountImplied => return (move s),
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CountIs(width) => { width as uint }
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};
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let strlen = str::char_len(s);
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if uwidth <= strlen { return (move s); }
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let mut padchar = ' ';
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let diff = uwidth - strlen;
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if have_flag(cv.flags, flag_left_justify) {
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let padstr = str::from_chars(vec::from_elem(diff, padchar));
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return s + padstr;
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}
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let {might_zero_pad, signed} = match mode {
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PadNozero => {might_zero_pad:false, signed:false},
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PadSigned => {might_zero_pad:true, signed:true },
|
|
PadFloat => {might_zero_pad:true, signed:true},
|
|
PadUnsigned => {might_zero_pad:true, signed:false}
|
|
};
|
|
pure fn have_precision(cv: Conv) -> bool {
|
|
return match cv.precision { CountImplied => false, _ => true };
|
|
}
|
|
let zero_padding = {
|
|
if might_zero_pad && have_flag(cv.flags, flag_left_zero_pad) &&
|
|
(!have_precision(cv) || mode == PadFloat) {
|
|
padchar = '0';
|
|
true
|
|
} else {
|
|
false
|
|
}
|
|
};
|
|
let padstr = str::from_chars(vec::from_elem(diff, padchar));
|
|
// This is completely heinous. If we have a signed value then
|
|
// potentially rip apart the intermediate result and insert some
|
|
// zeros. It may make sense to convert zero padding to a precision
|
|
// instead.
|
|
|
|
if signed && zero_padding && s.len() > 0 {
|
|
let head = str::shift_char(&mut s);
|
|
if head == '+' || head == '-' || head == ' ' {
|
|
let headstr = str::from_chars(vec::from_elem(1u, head));
|
|
return headstr + padstr + s;
|
|
}
|
|
else {
|
|
str::unshift_char(&mut s, head);
|
|
}
|
|
}
|
|
return padstr + s;
|
|
}
|
|
pub pure fn have_flag(flags: u32, f: u32) -> bool {
|
|
flags & f != 0
|
|
}
|
|
}
|
|
|
|
// Bulk of the tests are in src/test/run-pass/syntax-extension-fmt.rs
|
|
#[cfg(test)]
|
|
mod test {
|
|
#[test]
|
|
fn fmt_slice() {
|
|
let s = "abc";
|
|
let _s = fmt!("%s", s);
|
|
}
|
|
}
|
|
|
|
// Local Variables:
|
|
// mode: rust;
|
|
// fill-column: 78;
|
|
// indent-tabs-mode: nil
|
|
// c-basic-offset: 4
|
|
// buffer-file-coding-system: utf-8-unix
|
|
// End:
|