libc-top-half/musl/src/stdio/fmemopen.c

   1 #include "stdio_impl.h"
   2 #include <errno.h>
   3 #include <string.h>
   4 #include <stdlib.h>
   5 #include <inttypes.h>
   6 #include "libc.h"
   7
   8 struct cookie {
   9         size_t pos, len, size;
  10         unsigned char *buf;
  11         int mode;
  12 };
  13
  14 struct mem_FILE {
  15         FILE f;
  16         struct cookie c;
  17         unsigned char buf[UNGET+BUFSIZ], buf2[];
  18 };
  19
  20 static off_t mseek(FILE *f, off_t off, int whence)
  21 {
  22         ssize_t base;
  23         struct cookie *c = f->cookie;
  24         if (whence>2U) {
  25 fail:
  26                 errno = EINVAL;
  27                 return -1;
  28         }
  29 #ifdef __wasilibc_unmodified_upstream // WASI's SEEK_* constants have different values.
  30         base = (size_t [3]){0, c->pos, c->len}[whence];
  31 #else
  32         base = (size_t [3]) {
  33             [SEEK_SET] = 0,
  34             [SEEK_CUR] = c->pos,
  35             [SEEK_END] = c->len
  36         }[whence];
  37 #endif
  38         if (off < -base || off > (ssize_t)c->size-base) goto fail;
  39         return c->pos = base+off;
  40 }
  41
  42 static size_t mread(FILE *f, unsigned char *buf, size_t len)
  43 {
  44         struct cookie *c = f->cookie;
  45         size_t rem = c->len - c->pos;
  46         if (c->pos > c->len) rem = 0;
  47         if (len > rem) {
  48                 len = rem;
  49                 f->flags |= F_EOF;
  50         }
  51         memcpy(buf, c->buf+c->pos, len);
  52         c->pos += len;
  53         rem -= len;
  54         if (rem > f->buf_size) rem = f->buf_size;
  55         f->rpos = f->buf;
  56         f->rend = f->buf + rem;
  57         memcpy(f->rpos, c->buf+c->pos, rem);
  58         c->pos += rem;
  59         return len;
  60 }
  61
  62 static size_t mwrite(FILE *f, const unsigned char *buf, size_t len)
  63 {
  64         struct cookie *c = f->cookie;
  65         size_t rem;
  66         size_t len2 = f->wpos - f->wbase;
  67         if (len2) {
  68                 f->wpos = f->wbase;
  69                 if (mwrite(f, f->wpos, len2) < len2) return 0;
  70         }
  71         if (c->mode == 'a') c->pos = c->len;
  72         rem = c->size - c->pos;
  73         if (len > rem) len = rem;
  74         memcpy(c->buf+c->pos, buf, len);
  75         c->pos += len;
  76         if (c->pos > c->len) {
  77                 c->len = c->pos;
  78                 if (c->len < c->size) c->buf[c->len] = 0;
  79                 else if ((f->flags&F_NORD) && c->size) c->buf[c->size-1] = 0;
  80         }
  81         return len;
  82 }
  83
  84 static int mclose(FILE *m)
  85 {
  86         return 0;
  87 }
  88
  89 FILE *fmemopen(void *restrict buf, size_t size, const char *restrict mode)
  90 {
  91         struct mem_FILE *f;
  92         int plus = !!strchr(mode, '+');
  93
  94         if (!strchr("rwa", *mode)) {
  95                 errno = EINVAL;
  96                 return 0;
  97         }
  98
  99         if (!buf && size > PTRDIFF_MAX) {
 100                 errno = ENOMEM;
 101                 return 0;
 102         }
 103
 104         f = malloc(sizeof *f + (buf?0:size));
 105         if (!f) return 0;
 106         memset(&f->f, 0, sizeof f->f);
 107         f->f.cookie = &f->c;
 108         f->f.fd = -1;
 109         f->f.lbf = EOF;
 110         f->f.buf = f->buf + UNGET;
 111         f->f.buf_size = sizeof f->buf - UNGET;
 112         if (!buf) {
 113                 buf = f->buf2;;
 114                 memset(buf, 0, size);
 115         }
 116
 117         memset(&f->c, 0, sizeof f->c);
 118         f->c.buf = buf;
 119         f->c.size = size;
 120         f->c.mode = *mode;
 121
 122         if (!plus) f->f.flags = (*mode == 'r') ? F_NOWR : F_NORD;
 123         if (*mode == 'r') f->c.len = size;
 124         else if (*mode == 'a') f->c.len = f->c.pos = strnlen(buf, size);
 125         else if (plus) *f->c.buf = 0;
 126
 127         f->f.read = mread;
 128         f->f.write = mwrite;
 129         f->f.seek = mseek;
 130         f->f.close = mclose;
 131
 132 #if defined(__wasilibc_unmodified_upstream) || defined(_REENTRANT)
 133         if (!libc.threaded) f->f.lock = -1;
 134 #endif
 135
 136         return __ofl_add(&f->f);
 137 }