460 lines
16 KiB
Rust
460 lines
16 KiB
Rust
#[doc(hidden)];
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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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import 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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mod ct {
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enum signedness { signed, unsigned, }
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enum caseness { case_upper, case_lower, }
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enum ty {
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ty_bool,
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ty_str,
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ty_char,
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ty_int(signedness),
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ty_bits,
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ty_hex(caseness),
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ty_octal,
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ty_float,
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ty_poly,
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}
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enum flag {
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flag_left_justify,
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flag_left_zero_pad,
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flag_space_for_sign,
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flag_sign_always,
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flag_alternate,
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}
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enum count {
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count_is(int),
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count_is_param(int),
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count_is_next_param,
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count_implied,
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}
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// A formatted conversion from an expression to a string
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type conv =
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{param: option<int>,
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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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enum piece { piece_string(~str), piece_conv(conv), }
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type error_fn = fn@(~str) -> ! ;
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fn parse_fmt_string(s: ~str, error: error_fn) -> ~[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: ~[piece]) -> ~str {
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if str::len(buf) > 0u {
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let piece = piece_string(buf);
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vec::push(pieces, piece);
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}
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return ~"";
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}
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let mut i = 0u;
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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 += 1u;
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if i >= lim {
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error(~"unterminated conversion at end of string");
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}
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let curr2 = str::slice(s, i, i+1u);
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if curr2 == ~"%" {
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buf += curr2;
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i += 1u;
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} else {
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buf = flush_buf(buf, pieces);
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let rs = parse_conversion(s, i, lim, error);
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vec::push(pieces, 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(buf, pieces);
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return pieces;
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}
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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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fn parse_conversion(s: ~str, i: uint, lim: uint, error: error_fn) ->
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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, error);
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return {piece:
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piece_conv({param: parm.param,
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flags: 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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fn parse_parameter(s: ~str, i: uint, lim: uint) ->
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{param: option<int>, 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 as int), next: j + 1u}
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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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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: 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 = 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(curr, rest), next: j};
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}
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let more = |x| more_(x, 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(flag_left_justify)
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} else if f == '0' as u8 {
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more(flag_left_zero_pad)
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} else if f == ' ' as u8 {
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more(flag_space_for_sign)
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} else if f == '+' as u8 {
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more(flag_sign_always)
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} else if f == '#' as u8 {
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more(flag_alternate)
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} else { {flags: noflags, next: i} };
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}
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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: count_implied, next: i}
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} else if s[i] == '*' as u8 {
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let param = parse_parameter(s, i + 1u, lim);
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let j = param.next;
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match param.param {
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none => {count: count_is_next_param, next: j},
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some(n) => {count: count_is_param(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: count_implied, next: i},
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some(num) => {
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count: count_is(num.num as int),
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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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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: count_implied, 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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count_implied => {count: count_is(0), next: count.next},
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_ => count
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}
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} else { {count: count_implied, next: i} };
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}
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fn parse_type(s: ~str, i: uint, lim: uint, error: error_fn) ->
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{ty: ty, next: uint} {
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if i >= lim { error(~"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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ty_bool
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} else if tstr == ~"s" {
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ty_str
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} else if tstr == ~"c" {
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ty_char
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} else if tstr == ~"d" || tstr == ~"i" {
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ty_int(signed)
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} else if tstr == ~"u" {
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ty_int(unsigned)
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} else if tstr == ~"x" {
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ty_hex(case_lower)
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} else if tstr == ~"X" {
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ty_hex(case_upper)
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} else if tstr == ~"t" {
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ty_bits
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} else if tstr == ~"o" {
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ty_octal
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} else if tstr == ~"f" {
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ty_float
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} else if tstr == ~"?" {
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ty_poly
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} else { error(~"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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mod rt {
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const flag_none : u32 = 0u32;
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const flag_left_justify : u32 = 0b00000000000000000000000000000001u32;
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const flag_left_zero_pad : u32 = 0b00000000000000000000000000000010u32;
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const flag_space_for_sign : u32 = 0b00000000000000000000000000000100u32;
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const flag_sign_always : u32 = 0b00000000000000000000000000001000u32;
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const flag_alternate : u32 = 0b00000000000000000000000000010000u32;
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enum count { count_is(int), count_implied, }
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enum ty { ty_default, ty_bits, ty_hex_upper, ty_hex_lower, ty_octal, }
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type conv = {flags: u32, width: count, precision: count, ty: ty};
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pure fn conv_int(cv: conv, i: int) -> ~str {
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let radix = 10u;
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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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unchecked { str::unshift_char(s, '+') };
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} else if have_flag(cv.flags, flag_space_for_sign) {
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unchecked { str::unshift_char(s, ' ') };
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}
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}
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return unchecked { pad(cv, s, pad_signed) };
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}
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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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ty_default => uint_to_str_prec(u, 10u, prec),
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ty_hex_lower => uint_to_str_prec(u, 16u, prec),
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ty_hex_upper => str::to_upper(uint_to_str_prec(u, 16u, prec)),
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ty_bits => uint_to_str_prec(u, 2u, prec),
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ty_octal => uint_to_str_prec(u, 8u, prec)
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};
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return unchecked { pad(cv, rs, pad_unsigned) };
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}
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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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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 unchecked { pad(cv, s, pad_nozero) };
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}
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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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count_implied => s.to_unique(),
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count_is(max) => if max as uint < str::char_len(s) {
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str::substr(s, 0u, max as uint)
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} else {
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s.to_unique()
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}
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};
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return unchecked { pad(cv, unpadded, pad_nozero) };
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}
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pure fn conv_float(cv: conv, f: float) -> ~str {
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let (to_str, digits) = match cv.precision {
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count_is(c) => (float::to_str_exact, c as uint),
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count_implied => (float::to_str, 6u)
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};
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let mut s = unchecked { 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 unchecked { pad(cv, s, pad_float) };
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}
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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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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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pure fn uint_to_str_prec(num: uint, radix: uint, 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 { s }
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};
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}
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pure fn get_int_precision(cv: conv) -> uint {
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return match cv.precision {
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count_is(c) => c as uint,
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count_implied => 1u
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};
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}
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enum pad_mode { pad_signed, pad_unsigned, pad_nozero, pad_float }
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fn pad(cv: conv, &s: ~str, mode: pad_mode) -> ~str {
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let uwidth : uint = match cv.width {
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count_implied => return s,
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count_is(width) => {
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// FIXME: width should probably be uint (see Issue #1996)
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width as uint
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}
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};
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let strlen = str::char_len(s);
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if uwidth <= strlen { return 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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pad_nozero => {might_zero_pad:false, signed:false},
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pad_signed => {might_zero_pad:true, signed:true },
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pad_float => {might_zero_pad:true, signed:true},
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pad_unsigned => {might_zero_pad:true, signed:false}
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};
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pure fn have_precision(cv: conv) -> bool {
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return match cv.precision { count_implied => false, _ => true };
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}
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let zero_padding = {
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if might_zero_pad && have_flag(cv.flags, flag_left_zero_pad) &&
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(!have_precision(cv) || mode == pad_float) {
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padchar = '0';
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true
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} else {
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false
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}
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};
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let padstr = str::from_chars(vec::from_elem(diff, padchar));
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// This is completely heinous. If we have a signed value then
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// potentially rip apart the intermediate result and insert some
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// zeros. It may make sense to convert zero padding to a precision
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// instead.
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if signed && zero_padding && str::len(s) > 0u {
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let head = str::shift_char(s);
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if head == '+' || head == '-' || head == ' ' {
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let headstr = str::from_chars(vec::from_elem(1u, head));
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return headstr + padstr + s;
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}
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else {
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str::unshift_char(s, head);
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}
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}
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return padstr + s;
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}
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pure fn have_flag(flags: u32, f: u32) -> bool {
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flags & f != 0
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}
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}
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#[cfg(test)]
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mod test {
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#[test]
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fn fmt_slice() {
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let s = "abc";
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let _s = fmt!{"%s", s};
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}
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}
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// Local Variables:
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// mode: rust;
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// fill-column: 78;
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// indent-tabs-mode: nil
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// c-basic-offset: 4
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// buffer-file-coding-system: utf-8-unix
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// End:
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