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