461 lines
15 KiB
Rust
461 lines
15 KiB
Rust
/*
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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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// FIXME: More types
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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] unsafe {
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let pieces: [piece] = [];
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let lim = str::byte_len(s);
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let buf = "";
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fn flush_buf(buf: str, &pieces: [piece]) -> str {
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if str::byte_len(buf) > 0u {
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let piece = piece_string(buf);
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pieces += [piece];
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}
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ret "";
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}
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let i = 0u;
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while i < lim {
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let curr = str::unsafe::slice_bytes(s, i, i+1u);
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if str::eq(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::unsafe::slice_bytes(s, i, i+1u);
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if str::eq(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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pieces += [rs.piece];
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i = rs.next;
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}
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} else { buf += curr; i += 1u; }
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}
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buf = flush_buf(buf, pieces);
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ret 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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if i >= lim { ret none; }
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let c = s[i];
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if !('0' as u8 <= c && c <= '9' as u8) { ret option::none; }
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let n = (c - ('0' as u8)) as uint;
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ret alt peek_num(s, i + 1u, lim) {
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none { some({num: n, next: i + 1u}) }
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some(next) {
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let m = next.num;
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let j = next.next;
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some({num: n * 10u + m, next: j})
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}
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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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ret {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 { ret {param: none, next: i}; }
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let num = peek_num(s, i, lim);
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ret alt 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 { ret {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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ret {flags: curr + rest, next: j};
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}
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let more = bind more_(_, s, i, lim);
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let f = s[i];
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ret 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) -> {count: count, next: uint} {
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ret 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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alt 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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alt 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), 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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ret 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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alt 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} unsafe {
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if i >= lim { error("missing type in conversion"); }
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let tstr = str::unsafe::slice_bytes(s, i, i+1u);
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// TODO: 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 str::eq(tstr, "b") {
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ty_bool
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} else if str::eq(tstr, "s") {
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ty_str
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} else if str::eq(tstr, "c") {
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ty_char
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} else if str::eq(tstr, "d") || str::eq(tstr, "i") {
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ty_int(signed)
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} else if str::eq(tstr, "u") {
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ty_int(unsigned)
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} else if str::eq(tstr, "x") {
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ty_hex(case_lower)
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} else if str::eq(tstr, "X") {
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ty_hex(case_upper)
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} else if str::eq(tstr, "t") {
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ty_bits
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} else if str::eq(tstr, "o") {
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ty_octal
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} else if str::eq(tstr, "f") {
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ty_float
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} else if str::eq(tstr, "?") {
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ty_poly
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} else { error("unknown type in conversion: " + tstr) };
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ret {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 this way, I think.
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mod rt {
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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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// FIXME: This is a hack to avoid creating 0-length vec exprs,
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// which have some difficulty typechecking currently. See
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// comments in front::extfmt::make_flags
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flag_none,
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}
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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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// FIXME: May not want to use a vector here for flags;
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// instead just use a bool per flag
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type conv = {flags: [flag], width: count, precision: count, ty: ty};
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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 s = 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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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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ret pad(cv, s, pad_signed);
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}
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fn conv_uint(cv: conv, u: uint) -> str {
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let prec = get_int_precision(cv);
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let rs =
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alt 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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ret pad(cv, rs, pad_unsigned);
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}
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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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ret conv_str(cv, s);
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}
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fn conv_char(cv: conv, c: char) -> str {
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ret pad(cv, str::from_char(c), pad_nozero);
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}
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fn conv_str(cv: conv, s: str) -> str unsafe {
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// For strings, precision is the maximum characters
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// displayed
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let unpadded =
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alt cv.precision {
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count_implied { s }
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count_is(max) {
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if max as uint < str::char_len(s) {
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str::substr(s, 0u, max as uint)
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} else { s }
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}
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};
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ret pad(cv, unpadded, pad_nozero);
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}
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fn conv_float(cv: conv, f: float) -> str {
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let (to_str, digits) = alt 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 s = 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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ret pad(cv, s, pad_signed);
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}
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fn conv_poly<T>(cv: conv, v: T) -> str {
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let s = sys::log_str(v);
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ret 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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fn int_to_str_prec(num: int, radix: uint, prec: uint) -> str {
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ret 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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fn uint_to_str_prec(num: uint, radix: uint, prec: uint) -> str {
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ret 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_init_elt(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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fn get_int_precision(cv: conv) -> uint {
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ret alt 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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// FIXME: This might be useful in str: but needs to be utf8 safe first
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fn str_init_elt(n_elts: uint, c: char) -> str {
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let svec = vec::init_elt::<u8>(n_elts, c as u8);
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ret str::from_bytes(svec);
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}
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enum pad_mode { pad_signed, pad_unsigned, pad_nozero, }
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fn pad(cv: conv, s: str, mode: pad_mode) -> str unsafe {
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let uwidth;
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alt cv.width {
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count_implied { ret s; }
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count_is(width) {
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// FIXME: Maybe width should be uint
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uwidth = 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 { ret s; }
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let 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_init_elt(diff, padchar);
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ret s + padstr;
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}
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let might_zero_pad = false;
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let signed = false;
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alt mode {
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pad_nozero {
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// fallthrough
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}
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pad_signed { might_zero_pad = true; signed = true; }
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pad_unsigned { might_zero_pad = true; }
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}
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fn have_precision(cv: conv) -> bool {
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ret alt cv.precision { count_implied { false } _ { true } };
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}
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let zero_padding = false;
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if might_zero_pad && have_flag(cv.flags, flag_left_zero_pad) &&
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!have_precision(cv) {
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padchar = '0';
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zero_padding = true;
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}
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let padstr = str_init_elt(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::byte_len(s) > 0u {
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let head = s[0];
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if head == '+' as u8 || head == '-' as u8 || head == ' ' as u8 {
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let headstr = str::from_bytes([head]);
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// FIXME: not UTF-8 safe
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let bytelen = str::byte_len(s);
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let numpart = str::unsafe::slice_bytes(s, 1u, bytelen);
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ret headstr + padstr + numpart;
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}
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}
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ret padstr + s;
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}
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fn have_flag(flags: [flag], f: flag) -> bool {
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for candidate: flag in flags { if candidate == f { ret true; } }
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ret false;
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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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