Commit 2fc78e700cc4684c1e5899d7a4a619da1e3e3679
2011-07-08T23:01:37
posix: Portable `vsnprintf` Our good, lovely folks at Microsoft decided that there was no good reason to make `vsnprintf` compilant with the C standard, so that function in Windows returns -1 on overflow, instead of returning the actual byte count needed to write the full string. We now handle this situation more gracefully with the POSIX compatibility layer, by returning the needed byte size using an auxiliary method instead of blindly resizing the target buffer until it fits. This means we can now support `printf`s of any size by allocating a temporary buffer. That's good.
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diff --git a/src/filebuf.c b/src/filebuf.c
index acfdcd1..86a643d 100644
--- a/src/filebuf.c
+++ b/src/filebuf.c
@@ -360,29 +360,48 @@ int git_filebuf_reserve(git_filebuf *file, void **buffer, size_t len)
int git_filebuf_printf(git_filebuf *file, const char *format, ...)
{
va_list arglist;
- size_t space_left = file->buf_size - file->buf_pos;
+ size_t space_left;
int len, error;
+ char *tmp_buffer;
- va_start(arglist, format);
- len = vsnprintf((char *)file->buffer + file->buf_pos, space_left, format, arglist);
- va_end(arglist);
+ space_left = file->buf_size - file->buf_pos;
+
+ do {
+ va_start(arglist, format);
+ len = p_vsnprintf((char *)file->buffer + file->buf_pos, space_left, format, arglist);
+ va_end(arglist);
+
+ if (len < 0)
+ return git__throw(GIT_EOSERR, "Failed to format string");
+
+ if ((size_t)len <= space_left) {
+ file->buf_pos += len;
+ return GIT_SUCCESS;
+ }
- if (len < 0 || (size_t)len >= space_left) {
if ((error = flush_buffer(file)) < GIT_SUCCESS)
return git__rethrow(error, "Failed to output to buffer");
space_left = file->buf_size - file->buf_pos;
- va_start(arglist, format);
- len = vsnprintf((char *)file->buffer + file->buf_pos, space_left, format, arglist);
- va_end(arglist);
+ } while ((size_t)len <= space_left);
- if (len < 0 || (size_t)len > file->buf_size)
- return GIT_ENOMEM;
+ tmp_buffer = git__malloc(len + 1);
+ if (!tmp_buffer)
+ return GIT_ENOMEM;
+
+ va_start(arglist, format);
+ len = p_vsnprintf(tmp_buffer, len + 1, format, arglist);
+ va_end(arglist);
+
+ if (len < 0) {
+ free(tmp_buffer);
+ return git__throw(GIT_EOSERR, "Failed to format string");
}
- file->buf_pos += len;
- return GIT_SUCCESS;
+ error = git_filebuf_write(file, tmp_buffer, len);
+ free(tmp_buffer);
+ return error;
}
diff --git a/src/unix/posix.h b/src/unix/posix.h
index d52aa09..16daf15 100644
--- a/src/unix/posix.h
+++ b/src/unix/posix.h
@@ -12,5 +12,6 @@
#define p_fsync(fd) fsync(fd)
#define p_realpath(p, po) realpath(p, po)
#define p_fnmatch(p, s, f) fnmatch(p, s, f)
+#define p_vsnprintf(b, c, f, a) vsnprintf(b, c, f, a)
#endif
diff --git a/src/win32/posix.c b/src/win32/posix.c
index dfa4e1a..c4d9eb3 100644
--- a/src/win32/posix.c
+++ b/src/win32/posix.c
@@ -209,3 +209,12 @@ char *p_realpath(const char *orig_path, char *buffer)
return buffer;
}
+int p_vsnprintf(char *buffer, size_t count, const char *format, va_list argptr)
+{
+#ifdef _MSV_VER
+ int len = _vsnprintf(buffer, count, format, argptr);
+ return (len < 0) ? _vscprintf(format, argptr) : len;
+#else /* MinGW */
+ return vsnprintf(buffer, count, format, argptr);
+#endif
+}
diff --git a/src/win32/posix.h b/src/win32/posix.h
index 503c5d8..efac68e 100644
--- a/src/win32/posix.h
+++ b/src/win32/posix.h
@@ -23,5 +23,6 @@ extern int p_lstat(const char *file_name, struct stat *buf);
extern int p_readlink(const char *link, char *target, size_t target_len);
extern int p_hide_directory__w32(const char *path);
extern char *p_realpath(const char *orig_path, char *buffer);
+extern int p_vsnprintf(char *buffer, size_t count, const char *format, va_list argptr);
#endif