Revision 56d7c27af1f8aa7519f165f6c022732e64db3716 authored by Jeff King on 26 May 2011, 16:30:27 UTC, committed by Junio C Hamano on 26 May 2011, 20:54:18 UTC
The read_in_full function repeatedly calls read() to fill a
buffer. If the first read() returns an error, we notify the
caller by returning the error. However, if we read some data
and then get an error on a subsequent read, we simply return
the amount of data that we did read, and the caller is
unaware of the error.
This makes the tradeoff that seeing the partial data is more
important than the fact that an error occurred. In practice,
this is generally not the case; we care more if an error
occurred, and should throw away any partial data.
I audited the current callers. In most cases, this will make
no difference at all, as they do:
if (read_in_full(fd, buf, size) != size)
error("short read");
However, it will help in a few cases:
1. In sha1_file.c:index_stream, we would fail to notice
errors in the incoming stream.
2. When reading symbolic refs in resolve_ref, we would
fail to notice errors and potentially use a truncated
ref name.
3. In various places, we will get much better error
messages. For example, callers of safe_read would
erroneously print "the remote end hung up unexpectedly"
instead of showing the read error.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 09ffc70
delta.h
#ifndef DELTA_H
#define DELTA_H
/* opaque object for delta index */
struct delta_index;
/*
* create_delta_index: compute index data from given buffer
*
* This returns a pointer to a struct delta_index that should be passed to
* subsequent create_delta() calls, or to free_delta_index(). A NULL pointer
* is returned on failure. The given buffer must not be freed nor altered
* before free_delta_index() is called. The returned pointer must be freed
* using free_delta_index().
*/
extern struct delta_index *
create_delta_index(const void *buf, unsigned long bufsize);
/*
* free_delta_index: free the index created by create_delta_index()
*
* Given pointer must be what create_delta_index() returned, or NULL.
*/
extern void free_delta_index(struct delta_index *index);
/*
* sizeof_delta_index: returns memory usage of delta index
*
* Given pointer must be what create_delta_index() returned, or NULL.
*/
extern unsigned long sizeof_delta_index(struct delta_index *index);
/*
* create_delta: create a delta from given index for the given buffer
*
* This function may be called multiple times with different buffers using
* the same delta_index pointer. If max_delta_size is non-zero and the
* resulting delta is to be larger than max_delta_size then NULL is returned.
* On success, a non-NULL pointer to the buffer with the delta data is
* returned and *delta_size is updated with its size. The returned buffer
* must be freed by the caller.
*/
extern void *
create_delta(const struct delta_index *index,
const void *buf, unsigned long bufsize,
unsigned long *delta_size, unsigned long max_delta_size);
/*
* diff_delta: create a delta from source buffer to target buffer
*
* If max_delta_size is non-zero and the resulting delta is to be larger
* than max_delta_size then NULL is returned. On success, a non-NULL
* pointer to the buffer with the delta data is returned and *delta_size is
* updated with its size. The returned buffer must be freed by the caller.
*/
static inline void *
diff_delta(const void *src_buf, unsigned long src_bufsize,
const void *trg_buf, unsigned long trg_bufsize,
unsigned long *delta_size, unsigned long max_delta_size)
{
struct delta_index *index = create_delta_index(src_buf, src_bufsize);
if (index) {
void *delta = create_delta(index, trg_buf, trg_bufsize,
delta_size, max_delta_size);
free_delta_index(index);
return delta;
}
return NULL;
}
/*
* patch_delta: recreate target buffer given source buffer and delta data
*
* On success, a non-NULL pointer to the target buffer is returned and
* *trg_bufsize is updated with its size. On failure a NULL pointer is
* returned. The returned buffer must be freed by the caller.
*/
extern void *patch_delta(const void *src_buf, unsigned long src_size,
const void *delta_buf, unsigned long delta_size,
unsigned long *dst_size);
/* the smallest possible delta size is 4 bytes */
#define DELTA_SIZE_MIN 4
/*
* This must be called twice on the delta data buffer, first to get the
* expected source buffer size, and again to get the target buffer size.
*/
static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
const unsigned char *top)
{
const unsigned char *data = *datap;
unsigned long cmd, size = 0;
int i = 0;
do {
cmd = *data++;
size |= (cmd & 0x7f) << i;
i += 7;
} while (cmd & 0x80 && data < top);
*datap = data;
return size;
}
#endif
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