d2e061a2bd
null termination is only added when current size grows. in update modes, null termination is not added if it does not fit (i.e. it is not allowed to clobber data). these rules make very little sense, but that's how it goes..
116 lines
2.3 KiB
C
116 lines
2.3 KiB
C
#include "stdio_impl.h"
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struct cookie {
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size_t pos, len, size;
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unsigned char *buf;
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int mode;
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};
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static off_t mseek(FILE *f, off_t off, int whence)
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{
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ssize_t base;
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struct cookie *c = f->cookie;
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if (whence>2U) {
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fail:
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errno = EINVAL;
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return -1;
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}
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base = (size_t [3]){0, c->pos, c->len}[whence];
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if (off < -base || off > (ssize_t)c->size-base) goto fail;
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return c->pos = base+off;
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}
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static size_t mread(FILE *f, unsigned char *buf, size_t len)
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{
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struct cookie *c = f->cookie;
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size_t rem = c->len - c->pos;
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if (c->pos > c->len) rem = 0;
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if (len > rem) {
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len = rem;
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f->flags |= F_EOF;
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}
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memcpy(buf, c->buf+c->pos, len);
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c->pos += len;
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rem -= len;
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if (rem > f->buf_size) rem = f->buf_size;
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f->rpos = f->buf;
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f->rend = f->buf + rem;
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memcpy(f->rpos, c->buf+c->pos, rem);
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c->pos += rem;
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return len;
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}
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static size_t mwrite(FILE *f, const unsigned char *buf, size_t len)
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{
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struct cookie *c = f->cookie;
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size_t rem;
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size_t len2 = f->wpos - f->wbase;
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if (len2) {
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f->wpos = f->wbase;
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if (mwrite(f, f->wpos, len2) < len2) return 0;
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}
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if (c->mode == 'a') c->pos = c->len;
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rem = c->size - c->pos;
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if (len > rem) len = rem;
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memcpy(c->buf+c->pos, buf, len);
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c->pos += len;
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if (c->pos > c->len) {
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c->len = c->pos;
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if (c->len < c->size) c->buf[c->len] = 0;
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else if ((f->flags&F_NORD) && c->size) c->buf[c->size-1] = 0;
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}
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return len;
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}
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static int mclose(FILE *m)
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{
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return 0;
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}
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FILE *fmemopen(void *buf, size_t size, const char *mode)
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{
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FILE *f;
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struct cookie *c;
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int plus = !!strchr(mode, '+');
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if (!size || !strchr("rwa", *mode)) {
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errno = EINVAL;
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return 0;
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}
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if (!buf && size > SIZE_MAX-sizeof(FILE)-BUFSIZ-UNGET) {
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errno = ENOMEM;
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return 0;
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}
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f = calloc(sizeof *f + sizeof *c + UNGET + BUFSIZ + (buf?0:size), 1);
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if (!f) return 0;
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f->cookie = c = (void *)(f+1);
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f->fd = -1;
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f->lbf = EOF;
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f->buf = (unsigned char *)(c+1) + UNGET;
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f->buf_size = BUFSIZ;
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if (!buf) buf = f->buf + BUFSIZ;
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c->buf = buf;
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c->size = size;
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c->mode = *mode;
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if (!plus) f->flags = (*mode == 'r') ? F_NOWR : F_NORD;
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if (*mode == 'r') c->len = size;
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else if (*mode == 'a') c->len = c->pos = strnlen(buf, size);
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f->read = mread;
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f->write = mwrite;
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f->seek = mseek;
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f->close = mclose;
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if (!libc.threaded) {
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f->lock = -1;
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f->next = libc.ofl_head;
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if (libc.ofl_head) libc.ofl_head->prev = f;
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libc.ofl_head = f;
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}
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return f;
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}
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