557 lines
16 KiB
Rust
557 lines
16 KiB
Rust
/* The 'fmt' extension is modeled on the posix printf system.
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*
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* A posix conversion ostensibly looks like this:
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*
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* %[parameter][flags][width][.precision][length]type
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*
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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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*
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* %[parameter][flags][width][.precision]type
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*
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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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*/
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import option.none;
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import option.some;
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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. Each
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* 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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tag signedness {
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signed;
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unsigned;
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}
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tag caseness {
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case_upper;
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case_lower;
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}
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tag 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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// FIXME: More types
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}
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tag 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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tag 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 = rec(option.t[int] param,
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vec[flag] flags,
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count width,
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count precision,
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ty ty);
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// A fragment of the output sequence
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tag piece {
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piece_string(str);
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piece_conv(conv);
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}
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fn parse_fmt_string(str s) -> vec[piece] {
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let vec[piece] pieces = vec();
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auto lim = _str.byte_len(s);
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auto buf = "";
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fn flush_buf(str buf, &vec[piece] pieces) -> str {
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if (_str.byte_len(buf) > 0u) {
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auto piece = piece_string(buf);
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pieces += vec(piece);
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}
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ret "";
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}
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auto i = 0u;
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while (i < lim) {
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auto curr = _str.substr(s, 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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log_err "unterminated conversion at end of string";
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fail;
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}
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auto curr2 = _str.substr(s, i, 1u);
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if (_str.eq(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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auto res = parse_conversion(s, i, lim);
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pieces += vec(res._0);
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i = res._1;
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}
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} else {
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buf += curr;
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i += 1u;
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}
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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(str s, uint i, uint lim) -> option.t[tup(uint, uint)] {
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if (i >= lim) {
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ret none[tup(uint, uint)];
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}
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auto c = s.(i);
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if (!('0' as u8 <= c && c <= '9' as u8)) {
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ret option.none[tup(uint, uint)];
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}
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auto n = (c - ('0' as u8)) as uint;
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alt (peek_num(s, i + 1u, lim)) {
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case (none[tup(uint, uint)]) {
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ret some[tup(uint, uint)](tup(n, i + 1u));
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}
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case (some[tup(uint, uint)](?next)) {
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auto m = next._0;
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auto j = next._1;
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ret some[tup(uint, uint)](tup(n * 10u + m, j));
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}
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}
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}
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fn parse_conversion(str s, uint i, uint lim) -> tup(piece, uint) {
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auto parm = parse_parameter(s, i, lim);
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auto flags = parse_flags(s, parm._1, lim);
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auto width = parse_count(s, flags._1, lim);
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auto prec = parse_precision(s, width._1, lim);
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auto ty = parse_type(s, prec._1, lim);
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ret tup(piece_conv(rec(param = parm._0,
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flags = flags._0,
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width = width._0,
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precision = prec._0,
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ty = ty._0)),
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ty._1);
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}
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fn parse_parameter(str s, uint i, uint lim) -> tup(option.t[int], uint) {
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if (i >= lim) {
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ret tup(none[int], i);
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}
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auto num = peek_num(s, i, lim);
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alt (num) {
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case (none[tup(uint, uint)]) {
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ret tup(none[int], i);
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}
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case (some[tup(uint, uint)](?t)) {
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auto n = t._0;
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auto j = t._1;
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if (j < lim && s.(j) == '$' as u8) {
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ret tup(some[int](n as int), j + 1u);
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}
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else {
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ret tup(none[int], i);
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}
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}
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}
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}
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fn parse_flags(str s, uint i, uint lim) -> tup(vec[flag], uint) {
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let vec[flag] noflags = vec();
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if (i >= lim) {
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ret tup(noflags, i);
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}
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fn more_(flag f, str s, uint i, uint lim) -> tup(vec[flag], uint) {
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auto next = parse_flags(s, i + 1u, lim);
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auto rest = next._0;
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auto j = next._1;
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let vec[flag] curr = vec(f);
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ret tup(curr + rest, j);
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}
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auto more = bind more_(_, s, i, lim);
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auto f = s.(i);
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if (f == ('-' as u8)) {
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ret more(flag_left_justify);
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} else if (f == ('0' as u8)) {
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ret more(flag_left_zero_pad);
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} else if (f == (' ' as u8)) {
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ret more(flag_space_for_sign);
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} else if (f == ('+' as u8)) {
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ret more(flag_sign_always);
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} else if (f == ('#' as u8)) {
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ret more(flag_alternate);
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} else {
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ret tup(noflags, i);
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}
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}
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fn parse_count(str s, uint i, uint lim) -> tup(count, uint) {
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if (i >= lim) {
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ret tup(count_implied, i);
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}
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if (s.(i) == ('*' as u8)) {
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auto param = parse_parameter(s, i + 1u, lim);
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auto j = param._1;
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alt (param._0) {
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case (none[int]) {
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ret tup(count_is_next_param, j);
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}
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case (some[int](?n)) {
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ret tup(count_is_param(n), j);
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}
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}
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} else {
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auto num = peek_num(s, i, lim);
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alt (num) {
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case (none[tup(uint, uint)]) {
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ret tup(count_implied, i);
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}
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case (some[tup(uint, uint)](?num)) {
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ret tup(count_is(num._0 as int), num._1);
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}
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}
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}
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}
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fn parse_precision(str s, uint i, uint lim) -> tup(count, uint) {
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if (i >= lim) {
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ret tup(count_implied, i);
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}
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if (s.(i) == '.' as u8) {
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auto 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._0) {
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case (count_implied) {
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ret tup(count_is(0), count._1);
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}
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case (_) {
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ret count;
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}
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}
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} else {
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ret tup(count_implied, i);
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}
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}
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fn parse_type(str s, uint i, uint lim) -> tup(ty, uint) {
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if (i >= lim) {
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log_err "missing type in conversion";
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fail;
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}
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auto t;
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auto tstr = _str.substr(s, i, 1u);
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if (_str.eq(tstr, "b")) {
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t = ty_bool;
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} else if (_str.eq(tstr, "s")) {
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t = ty_str;
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} else if (_str.eq(tstr, "c")) {
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t = ty_char;
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} else if (_str.eq(tstr, "d")
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|| _str.eq(tstr, "i")) {
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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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t = ty_int(signed);
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} else if (_str.eq(tstr, "u")) {
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t = ty_int(unsigned);
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} else if (_str.eq(tstr, "x")) {
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t = ty_hex(case_lower);
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} else if (_str.eq(tstr, "X")) {
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t = ty_hex(case_upper);
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} else if (_str.eq(tstr, "t")) {
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t = ty_bits;
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} else {
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log_err "unknown type in conversion";
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fail;
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}
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ret tup(t, 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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tag 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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tag count {
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count_is(int);
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count_implied;
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}
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tag ty {
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ty_default;
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ty_bits;
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ty_hex_upper;
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ty_hex_lower;
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}
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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 = rec(vec[flag] flags,
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count width,
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count precision,
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ty ty);
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fn conv_int(&conv cv, int i) -> str {
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auto radix = 10u;
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auto prec = get_int_precision(cv);
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auto 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(&conv cv, uint u) -> str {
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auto prec = get_int_precision(cv);
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auto res;
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alt (cv.ty) {
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case (ty_default) {
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res = uint_to_str_prec(u, 10u, prec);
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}
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case (ty_hex_lower) {
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res = uint_to_str_prec(u, 16u, prec);
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}
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case (ty_hex_upper) {
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res = _str.to_upper(uint_to_str_prec(u, 16u, prec));
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}
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case (ty_bits) {
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res = uint_to_str_prec(u, 2u, prec);
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}
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}
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ret pad(cv, res, pad_unsigned);
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}
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fn conv_bool(&conv cv, bool b) -> str {
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auto s;
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if (b) {
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s = "true";
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} else {
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s = "false";
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}
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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(&conv cv, char c) -> str {
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ret conv_str(cv, _str.from_char(c));
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}
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fn conv_str(&conv cv, str s) -> str {
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auto unpadded = s;
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alt (cv.precision) {
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case (count_implied) {
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}
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case (count_is(?max)) {
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// For strings, precision is the maximum characters displayed
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if (max as uint < _str.char_len(s)) {
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// FIXME: substr works on bytes, not chars!
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unpadded = _str.substr(s, 0u, max as uint);
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}
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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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// 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(int num, uint radix, uint prec) -> str {
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if (num < 0) {
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ret "-" + uint_to_str_prec((-num) as uint, radix, prec);
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} else {
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ret uint_to_str_prec(num as uint, radix, prec);
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}
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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(uint num, uint radix, uint prec) -> str {
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auto s;
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if (prec == 0u && num == 0u) {
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s = "";
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} else {
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s = _uint.to_str(num, radix);
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auto len = _str.char_len(s);
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if (len < prec) {
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auto diff = prec - len;
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auto pad = str_init_elt('0', diff);
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s = pad + s;
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}
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}
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ret s;
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}
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fn get_int_precision(&conv cv) -> uint {
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alt (cv.precision) {
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case (count_is(?c)) {
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ret c as uint;
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}
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case (count_implied) {
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ret 1u;
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}
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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(char c, uint n_elts) -> str {
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auto svec = _vec.init_elt[u8](c as u8, n_elts);
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// FIXME: Using unsafe_from_bytes because rustboot
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// can't figure out the is_utf8 predicate on from_bytes?
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ret _str.unsafe_from_bytes(svec);
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}
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tag pad_mode {
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pad_signed;
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pad_unsigned;
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pad_nozero;
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}
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fn pad(&conv cv, str s, pad_mode mode) -> str {
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auto uwidth;
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alt (cv.width) {
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case (count_implied) {
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ret s;
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}
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case (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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auto strlen = _str.char_len(s);
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if (uwidth <= strlen) {
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ret s;
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}
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auto padchar = ' ';
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auto diff = uwidth - strlen;
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if (have_flag(cv.flags, flag_left_justify)) {
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auto padstr = str_init_elt(padchar, diff);
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ret s + padstr;
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}
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auto might_zero_pad = false;
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auto signed = false;
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alt (mode) {
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case (pad_nozero) {
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// fallthrough
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}
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case (pad_signed) {
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might_zero_pad = true;
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signed = true;
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}
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case (pad_unsigned) {
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might_zero_pad = true;
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}
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}
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fn have_precision(&conv cv) -> bool {
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alt (cv.precision) {
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case (count_implied) {
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ret false;
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}
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case (_) {
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ret true;
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}
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}
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}
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auto zero_padding = false;
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if (might_zero_pad
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&& 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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auto padstr = str_init_elt(padchar, diff);
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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
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&& zero_padding
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&& _str.byte_len(s) > 0u
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&& s.(0) == '-' as u8) {
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auto bytelen = _str.byte_len(s);
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auto numpart = _str.substr(s, 1u, bytelen - 1u);
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ret "-" + padstr + numpart;
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} else {
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ret padstr + s;
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}
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}
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fn have_flag(vec[flag] flags, flag f) -> bool {
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for (flag candidate in flags) {
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if (candidate == f) {
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ret true;
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}
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}
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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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// compile-command: "make -k -C .. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
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// End:
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