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#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
size_t raw_write_fd(FILE *f, const unsigned char *s, size_t l) {
int rc = write(f->fd, (char *)s, l);
if (rc == -1) {
f->has_error = 1;
return 0;
}
return rc;
}
void fflush_fd(FILE *f) {
raw_write_fd(f, f->write_buffer, f->write_buffer_stored);
f->write_buffer_stored = 0;
}
size_t write_fd(FILE *f, const unsigned char *s, size_t l) {
if (!f->write_buffer) {
f->write_buffer = malloc(4096);
f->write_buffer_stored = 0;
}
if (l > 4096) {
return raw_write_fd(f, s, l);
}
if (f->write_buffer_stored + l > 4096) {
fflush_fd(f);
}
memcpy(f->write_buffer + f->write_buffer_stored, s, l);
f->write_buffer_stored += l;
return l;
}
size_t non_cache_read_fd(FILE *f, unsigned char *s, size_t l) {
int rc = read(f->fd, s, l);
if (rc == 0) {
f->is_eof = 1;
}
if (rc == -1) {
f->has_error = 1;
return 0;
}
return rc;
}
size_t read_fd(FILE *f, unsigned char *s, size_t l) {
if (0 == l) {
return 0;
}
// Skip using cache if the length being requested if longer than or
// equal to the cache block size. This avoids doing a bunch of extra
// syscalls
if (l >= 4096) {
// Invalidate the cache
f->read_buffer_stored = 0;
return non_cache_read_fd(f, s, l);
}
if (!f->read_buffer) {
f->read_buffer = malloc(4096);
f->read_buffer_stored = 0;
f->read_buffer_has_read = 0;
}
if (f->read_buffer_stored > 0) {
size_t read_len = min(l, f->read_buffer_stored);
memcpy(s, f->read_buffer + f->read_buffer_has_read, read_len);
f->read_buffer_stored -= read_len;
f->read_buffer_has_read += read_len;
s += read_len;
l -= read_len;
lseek(f->fd, read_len, SEEK_CUR);
return read_len + read_fd(f, s, l);
}
if (0 == f->read_buffer_stored) {
int offset = lseek(f->fd, 0, SEEK_CUR);
f->read_buffer_stored = non_cache_read_fd(f, f->read_buffer, 4096);
lseek(f->fd, offset, SEEK_SET);
f->read_buffer_has_read = 0;
if (0 == f->read_buffer_stored) {
return 0;
}
return read_fd(f, s, l);
}
assert(0);
return 0;
}
int seek_fd(FILE *stream, long offset, int whence) {
stream->read_buffer_stored = 0;
return lseek(stream->fd, offset, whence);
}
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