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7c6c7095b9
* gl/lib/mbbuf.h (mbbuf_get_char): Don't set G.len to 1, since mcel_err has already done it.
117 lines
3.3 KiB
C
117 lines
3.3 KiB
C
/* Buffering for multi-byte characters.
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Copyright (C) 2025 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Collin Funk. */
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#ifndef _MBBUF_H
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#define _MBBUF_H 1
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#ifndef _GL_INLINE_HEADER_BEGIN
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# error "Please include config.h first."
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#endif
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#include <stdio.h>
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#include <stddef.h>
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#include "mcel.h"
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#include "idx.h"
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_GL_INLINE_HEADER_BEGIN
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#ifndef MBBUF_INLINE
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# define MBBUF_INLINE _GL_INLINE
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#endif
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/* End of file. */
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#define MBBUF_EOF UINT32_MAX
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/* MBBUF_EOF should not be a valid character. */
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static_assert (MCEL_CHAR_MAX < MBBUF_EOF);
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typedef struct
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{
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char *buffer; /* Input buffer. */
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FILE *fp; /* Input file stream. */
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idx_t size; /* Number of bytes allocated for BUFFER. */
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idx_t length; /* Number of bytes with data in BUFFER. */
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idx_t offset; /* Current position in BUFFER. */
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} mbbuf_t;
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/* Initialize MBBUF with an allocated BUFFER of SIZE bytes and a file stream
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FP open for reading. SIZE must be greater than or equal to MCEL_LEN_MAX.
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*/
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MBBUF_INLINE void
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mbbuf_init (mbbuf_t *mbbuf, char *buffer, idx_t size, FILE *fp)
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{
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if (size < MCEL_LEN_MAX)
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unreachable ();
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mbbuf->buffer = buffer;
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mbbuf->fp = fp;
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mbbuf->size = size;
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mbbuf->length = 0;
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mbbuf->offset = 0;
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}
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/* Get the next character in the buffer, filling it from FP if necessary.
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If an invalid multi-byte character is seen, we assume the program wants to
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fall back to the read byte. */
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MBBUF_INLINE mcel_t
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mbbuf_get_char (mbbuf_t *mbbuf)
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{
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idx_t available = mbbuf->length - mbbuf->offset;
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/* Check if we need to fill the input buffer. */
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if (available < MCEL_LEN_MAX && ! feof (mbbuf->fp))
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{
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idx_t start;
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if (!(0 < available))
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start = 0;
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else
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{
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memmove (mbbuf->buffer, mbbuf->buffer + mbbuf->offset, available);
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start = available;
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}
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mbbuf->length = fread (mbbuf->buffer + start, 1, mbbuf->size - start,
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mbbuf->fp) + start;
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mbbuf->offset = 0;
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available = mbbuf->length - mbbuf->offset;
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}
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if (available <= 0)
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return (mcel_t) { .ch = MBBUF_EOF };
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mcel_t g = mcel_scan (mbbuf->buffer + mbbuf->offset,
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mbbuf->buffer + mbbuf->length);
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if (! g.err)
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mbbuf->offset += g.len;
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else
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{
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/* Assume the program will emit the byte, but keep the error flag. */
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g.ch = mbbuf->buffer[mbbuf->offset++];
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}
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return g;
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}
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/* Returns a pointer to the first byte in the previously read character from
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mbbuf_get_char. */
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MBBUF_INLINE char *
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mbbuf_char_offset (mbbuf_t *mbbuf, mcel_t g)
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{
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if (mbbuf->offset < g.len)
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unreachable ();
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return mbbuf->buffer + (mbbuf->offset - g.len);
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}
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_GL_INLINE_HEADER_END
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#endif
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