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/* libfmt/quote.c - C-string quoting for pico-fmt
*
* Copyright (C) 2025 Luke T. Shumaker <lukeshu@lukeshu.com>
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
#include <string.h> /* for strnlen() */
#include <stdint.h> /* for uint{n}_t() */
#include <libfmt/fmt.h>
enum quote {
QUOTE_NONE, /* c */
QUOTE_SIMPLE, /* \c */
QUOTE_U4, /* \uABCD */
QUOTE_U8, /* \UABCDABCD */
};
static inline enum quote needs_quote(uint32_t ch) {
if (ch == '\a' ||
ch == '\b' ||
ch == '\f' ||
ch == '\n' ||
ch == '\r' ||
ch == '\t' ||
ch == '\v' ||
ch == '\\' ||
ch == '\'' ||
ch == '"' ||
ch == '?')
return QUOTE_SIMPLE;
else if (' ' <= ch && ch <= '~')
return QUOTE_NONE;
else if (ch < 0x10000)
return QUOTE_U4;
else
return QUOTE_U8;
}
/**
* Quote a string to ASCII-only C syntax. Valid UTF-8 is quoted as
* short C-escape characters, \uABCD or \UABCDABCD; invalid UTF-8 is
* quoted as \xAB.
*/
static void libfmt_conv_quote(struct fmt_state *state) {
uint32_t ch;
uint8_t chlen;
const char *in = va_arg(*state->args, char*);
size_t in_len = strnlen(in, (state->flags & FMT_FLAG_PRECISION) ? state->precision : (size_t)-1);
size_t out_len = 2;
for (size_t pos = 0; pos < in_len;) {
if ((in[pos] & 0b10000000) == 0b00000000) { ch = in[pos] & 0b01111111; chlen = 1; }
else if ((in[pos] & 0b11100000) == 0b11000000) { ch = in[pos] & 0b00011111; chlen = 2; }
else if ((in[pos] & 0b11110000) == 0b11100000) { ch = in[pos] & 0b00001111; chlen = 3; }
else if ((in[pos] & 0b11111000) == 0b11110000) { ch = in[pos] & 0b00000111; chlen = 4; }
else goto measure_invalid_utf8;
if ((ch == 0 && chlen != 1) || pos + chlen > in_len) goto measure_invalid_utf8;
for (uint8_t i = 1; i < chlen; i++) {
if ((in[pos+i] & 0b11000000) != 0b10000000) goto measure_invalid_utf8;
ch = (ch << 6) | (in[pos+i] & 0b00111111);
}
if (ch > 0x10FFFF) goto measure_invalid_utf8;
pos += chlen;
switch (needs_quote(ch)) {
case QUOTE_NONE : out_len += 1; break;
case QUOTE_SIMPLE : out_len += 2; break;
case QUOTE_U4 : out_len += 6; break;
case QUOTE_U8 : out_len += 10; break;
}
continue;
measure_invalid_utf8:
pos++;
out_len += 4; /* \xAB */
}
if (!(state->flags & FMT_FLAG_LEFT)) {
for (size_t i = 0; i + out_len < state->width; i++) {
fmt_state_putchar(state, ' ');
}
}
fmt_state_putchar(state, '"');
for (size_t pos = 0; pos < in_len;) {
if ((in[pos] & 0b10000000) == 0b00000000) { ch = in[pos] & 0b01111111; chlen = 1; }
else if ((in[pos] & 0b11100000) == 0b11000000) { ch = in[pos] & 0b00011111; chlen = 2; }
else if ((in[pos] & 0b11110000) == 0b11100000) { ch = in[pos] & 0b00001111; chlen = 3; }
else if ((in[pos] & 0b11111000) == 0b11110000) { ch = in[pos] & 0b00000111; chlen = 4; }
else goto output_invalid_utf8;
if ((ch == 0 && chlen != 1) || pos + chlen > in_len) goto output_invalid_utf8;
for (uint8_t i = 1; i < chlen; i++) {
if ((in[pos+i] & 0b11000000) != 0b10000000) goto output_invalid_utf8;
ch = (ch << 6) | (in[pos+i] & 0b00111111);
}
if (ch > 0x10FFFF) goto output_invalid_utf8;
pos += chlen;
switch (needs_quote(ch)) {
case QUOTE_NONE:
fmt_state_putchar(state, ch);
break;
case QUOTE_SIMPLE:
fmt_state_putchar(state, '\\');
switch (ch) {
case '\a': fmt_state_putchar(state, 'a'); break;
case '\b': fmt_state_putchar(state, 'b'); break;
case '\f': fmt_state_putchar(state, 'f'); break;
case '\n': fmt_state_putchar(state, 'n'); break;
case '\r': fmt_state_putchar(state, 'r'); break;
case '\t': fmt_state_putchar(state, 't'); break;
case '\v': fmt_state_putchar(state, 'v'); break;
case '\\': fmt_state_putchar(state, '\\'); break;
case '\'': fmt_state_putchar(state, '\''); break;
case '"': fmt_state_putchar(state, '"'); break;
case '?': fmt_state_putchar(state, '?'); break;
}
break;
case QUOTE_U4:
fmt_state_putchar(state, '\\');
fmt_state_putchar(state, 'u');
fmt_state_putchar(state, (ch >> 12) & 0xF);
fmt_state_putchar(state, (ch >> 8) & 0xF);
fmt_state_putchar(state, (ch >> 4) & 0xF);
fmt_state_putchar(state, (ch >> 0) & 0xF);
break;
case QUOTE_U8:
fmt_state_putchar(state, '\\');
fmt_state_putchar(state, 'U');
fmt_state_putchar(state, (ch >> 28) & 0xF);
fmt_state_putchar(state, (ch >> 24) & 0xF);
fmt_state_putchar(state, (ch >> 20) & 0xF);
fmt_state_putchar(state, (ch >> 16) & 0xF);
fmt_state_putchar(state, (ch >> 12) & 0xF);
fmt_state_putchar(state, (ch >> 8) & 0xF);
fmt_state_putchar(state, (ch >> 4) & 0xF);
fmt_state_putchar(state, (ch >> 0) & 0xF);
break;
}
continue;
output_invalid_utf8:
fmt_state_putchar(state, '\\');
fmt_state_putchar(state, 'x');
fmt_state_putchar(state, (in[pos] >> 4) & 0xF);
fmt_state_putchar(state, (in[pos] >> 0) & 0xF);
pos++;
}
fmt_state_putchar(state, '"');
for (size_t i = 0; i + out_len < state->width; i++) {
fmt_state_putchar(state, ' ');
}
}
[[gnu::constructor]]
static void libfmt_install_quote(void) {
fmt_install('q', libfmt_conv_quote);
}
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