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#include <assert.h>
#include <stdio.h>
#include <unistd.h>
size_t write_fd(FILE *f, const unsigned char *s, size_t l) {
int rc = pwrite(f->fd, s, l, f->offset_in_file);
if (rc == -1) {
f->has_error = 1;
return 0;
}
f->offset_in_file += rc;
return rc;
}
size_t non_cache_read_fd(FILE *f, unsigned char *s, size_t l) {
int rc = pread(f->fd, s, l, f->offset_in_file);
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;
size_t rc = non_cache_read_fd(f, s, l);
f->offset_in_file += rc;
return rc;
}
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);
f->offset_in_file += read_len;
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;
return read_len + read_fd(f, s, l);
}
if (0 == f->read_buffer_stored) {
f->read_buffer_stored = non_cache_read_fd(f, f->read_buffer, 4096);
f->read_buffer_has_read = 0;
if (0 == f->read_buffer_stored) {
return 0;
}
return read_fd(f, s, l);
}
assert(0);
}
int seek_fd(FILE *stream, long offset, int whence) {
stream->read_buffer_stored = 0;
switch (whence) {
case SEEK_SET:
stream->offset_in_file = offset;
break;
case SEEK_CUR:
stream->offset_in_file += offset;
break;
case SEEK_END:
stream->offset_in_file = stream->file_size + offset;
break;
default:
assert(0);
break;
}
// FIXME: Error checking
return 0;
}
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