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![Jeff King](/assets/img/avatar_default.png)
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>
384 lines
8.1 KiB
C
384 lines
8.1 KiB
C
/*
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* Various trivial helper wrappers around standard functions
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*/
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#include "cache.h"
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static void do_nothing(size_t size)
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{
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}
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static void (*try_to_free_routine)(size_t size) = do_nothing;
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try_to_free_t set_try_to_free_routine(try_to_free_t routine)
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{
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try_to_free_t old = try_to_free_routine;
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if (!routine)
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routine = do_nothing;
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try_to_free_routine = routine;
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return old;
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}
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char *xstrdup(const char *str)
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{
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char *ret = strdup(str);
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if (!ret) {
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try_to_free_routine(strlen(str) + 1);
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ret = strdup(str);
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if (!ret)
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die("Out of memory, strdup failed");
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}
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return ret;
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}
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void *xmalloc(size_t size)
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{
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void *ret = malloc(size);
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if (!ret && !size)
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ret = malloc(1);
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if (!ret) {
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try_to_free_routine(size);
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ret = malloc(size);
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if (!ret && !size)
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ret = malloc(1);
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if (!ret)
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die("Out of memory, malloc failed (tried to allocate %lu bytes)",
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(unsigned long)size);
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}
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#ifdef XMALLOC_POISON
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memset(ret, 0xA5, size);
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#endif
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return ret;
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}
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void *xmallocz(size_t size)
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{
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void *ret;
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if (unsigned_add_overflows(size, 1))
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die("Data too large to fit into virtual memory space.");
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ret = xmalloc(size + 1);
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((char*)ret)[size] = 0;
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return ret;
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}
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/*
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* xmemdupz() allocates (len + 1) bytes of memory, duplicates "len" bytes of
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* "data" to the allocated memory, zero terminates the allocated memory,
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* and returns a pointer to the allocated memory. If the allocation fails,
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* the program dies.
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*/
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void *xmemdupz(const void *data, size_t len)
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{
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return memcpy(xmallocz(len), data, len);
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}
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char *xstrndup(const char *str, size_t len)
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{
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char *p = memchr(str, '\0', len);
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return xmemdupz(str, p ? p - str : len);
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}
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void *xrealloc(void *ptr, size_t size)
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{
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void *ret = realloc(ptr, size);
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if (!ret && !size)
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ret = realloc(ptr, 1);
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if (!ret) {
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try_to_free_routine(size);
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ret = realloc(ptr, size);
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if (!ret && !size)
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ret = realloc(ptr, 1);
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if (!ret)
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die("Out of memory, realloc failed");
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}
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return ret;
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}
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void *xcalloc(size_t nmemb, size_t size)
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{
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void *ret = calloc(nmemb, size);
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if (!ret && (!nmemb || !size))
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ret = calloc(1, 1);
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if (!ret) {
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try_to_free_routine(nmemb * size);
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ret = calloc(nmemb, size);
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if (!ret && (!nmemb || !size))
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ret = calloc(1, 1);
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if (!ret)
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die("Out of memory, calloc failed");
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}
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return ret;
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}
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/*
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* xread() is the same a read(), but it automatically restarts read()
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* operations with a recoverable error (EAGAIN and EINTR). xread()
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* DOES NOT GUARANTEE that "len" bytes is read even if the data is available.
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*/
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ssize_t xread(int fd, void *buf, size_t len)
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{
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ssize_t nr;
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while (1) {
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nr = read(fd, buf, len);
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if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
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continue;
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return nr;
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}
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}
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/*
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* xwrite() is the same a write(), but it automatically restarts write()
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* operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT
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* GUARANTEE that "len" bytes is written even if the operation is successful.
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*/
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ssize_t xwrite(int fd, const void *buf, size_t len)
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{
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ssize_t nr;
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while (1) {
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nr = write(fd, buf, len);
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if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
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continue;
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return nr;
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}
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}
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ssize_t read_in_full(int fd, void *buf, size_t count)
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{
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char *p = buf;
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ssize_t total = 0;
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while (count > 0) {
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ssize_t loaded = xread(fd, p, count);
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if (loaded < 0)
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return -1;
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if (loaded == 0)
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return total;
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count -= loaded;
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p += loaded;
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total += loaded;
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}
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return total;
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}
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ssize_t write_in_full(int fd, const void *buf, size_t count)
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{
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const char *p = buf;
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ssize_t total = 0;
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while (count > 0) {
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ssize_t written = xwrite(fd, p, count);
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if (written < 0)
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return -1;
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if (!written) {
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errno = ENOSPC;
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return -1;
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}
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count -= written;
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p += written;
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total += written;
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}
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return total;
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}
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int xdup(int fd)
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{
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int ret = dup(fd);
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if (ret < 0)
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die_errno("dup failed");
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return ret;
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}
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FILE *xfdopen(int fd, const char *mode)
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{
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FILE *stream = fdopen(fd, mode);
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if (stream == NULL)
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die_errno("Out of memory? fdopen failed");
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return stream;
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}
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int xmkstemp(char *template)
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{
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int fd;
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char origtemplate[PATH_MAX];
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strlcpy(origtemplate, template, sizeof(origtemplate));
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fd = mkstemp(template);
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if (fd < 0) {
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int saved_errno = errno;
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const char *nonrelative_template;
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if (!template[0])
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template = origtemplate;
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nonrelative_template = absolute_path(template);
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errno = saved_errno;
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die_errno("Unable to create temporary file '%s'",
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nonrelative_template);
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}
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return fd;
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}
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/* git_mkstemp() - create tmp file honoring TMPDIR variable */
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int git_mkstemp(char *path, size_t len, const char *template)
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{
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const char *tmp;
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size_t n;
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tmp = getenv("TMPDIR");
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if (!tmp)
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tmp = "/tmp";
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n = snprintf(path, len, "%s/%s", tmp, template);
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if (len <= n) {
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errno = ENAMETOOLONG;
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return -1;
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}
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return mkstemp(path);
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}
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/* git_mkstemps() - create tmp file with suffix honoring TMPDIR variable. */
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int git_mkstemps(char *path, size_t len, const char *template, int suffix_len)
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{
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const char *tmp;
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size_t n;
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tmp = getenv("TMPDIR");
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if (!tmp)
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tmp = "/tmp";
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n = snprintf(path, len, "%s/%s", tmp, template);
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if (len <= n) {
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errno = ENAMETOOLONG;
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return -1;
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}
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return mkstemps(path, suffix_len);
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}
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/* Adapted from libiberty's mkstemp.c. */
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#undef TMP_MAX
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#define TMP_MAX 16384
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int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
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{
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static const char letters[] =
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"abcdefghijklmnopqrstuvwxyz"
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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"0123456789";
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static const int num_letters = 62;
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uint64_t value;
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struct timeval tv;
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char *template;
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size_t len;
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int fd, count;
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len = strlen(pattern);
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if (len < 6 + suffix_len) {
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errno = EINVAL;
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return -1;
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}
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if (strncmp(&pattern[len - 6 - suffix_len], "XXXXXX", 6)) {
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errno = EINVAL;
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return -1;
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}
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/*
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* Replace pattern's XXXXXX characters with randomness.
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* Try TMP_MAX different filenames.
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*/
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gettimeofday(&tv, NULL);
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value = ((size_t)(tv.tv_usec << 16)) ^ tv.tv_sec ^ getpid();
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template = &pattern[len - 6 - suffix_len];
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for (count = 0; count < TMP_MAX; ++count) {
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uint64_t v = value;
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/* Fill in the random bits. */
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template[0] = letters[v % num_letters]; v /= num_letters;
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template[1] = letters[v % num_letters]; v /= num_letters;
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template[2] = letters[v % num_letters]; v /= num_letters;
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template[3] = letters[v % num_letters]; v /= num_letters;
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template[4] = letters[v % num_letters]; v /= num_letters;
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template[5] = letters[v % num_letters]; v /= num_letters;
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fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
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if (fd > 0)
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return fd;
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/*
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* Fatal error (EPERM, ENOSPC etc).
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* It doesn't make sense to loop.
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*/
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if (errno != EEXIST)
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break;
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/*
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* This is a random value. It is only necessary that
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* the next TMP_MAX values generated by adding 7777 to
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* VALUE are different with (module 2^32).
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*/
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value += 7777;
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}
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/* We return the null string if we can't find a unique file name. */
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pattern[0] = '\0';
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return -1;
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}
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int git_mkstemp_mode(char *pattern, int mode)
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{
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/* mkstemp is just mkstemps with no suffix */
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return git_mkstemps_mode(pattern, 0, mode);
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}
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int gitmkstemps(char *pattern, int suffix_len)
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{
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return git_mkstemps_mode(pattern, suffix_len, 0600);
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}
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int xmkstemp_mode(char *template, int mode)
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{
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int fd;
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char origtemplate[PATH_MAX];
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strlcpy(origtemplate, template, sizeof(origtemplate));
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fd = git_mkstemp_mode(template, mode);
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if (fd < 0) {
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int saved_errno = errno;
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const char *nonrelative_template;
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if (!template[0])
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template = origtemplate;
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nonrelative_template = absolute_path(template);
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errno = saved_errno;
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die_errno("Unable to create temporary file '%s'",
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nonrelative_template);
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}
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return fd;
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}
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static int warn_if_unremovable(const char *op, const char *file, int rc)
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{
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if (rc < 0) {
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int err = errno;
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if (ENOENT != err) {
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warning("unable to %s %s: %s",
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op, file, strerror(errno));
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errno = err;
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}
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}
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return rc;
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}
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int unlink_or_warn(const char *file)
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{
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return warn_if_unremovable("unlink", file, unlink(file));
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}
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int rmdir_or_warn(const char *file)
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{
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return warn_if_unremovable("rmdir", file, rmdir(file));
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}
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int remove_or_warn(unsigned int mode, const char *file)
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{
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return S_ISGITLINK(mode) ? rmdir_or_warn(file) : unlink_or_warn(file);
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}
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