Clean up gz* function return values.

In some cases the return values did not match the documentation,
or the documentation did not document all of the return values.
gzprintf() now consistently returns negative values on error,
which matches the behavior of the stdio fprintf() function.

1 files changed, 17 insertions, 15 deletions

diff --git a/gzwrite.c b/gzwrite.c
index 88d7167..2aaf4d5 100644
--- a/gzwrite.c
+++ b/gzwrite.c
@@ -12,7 +12,8 @@ static int gz_comp(gz_statep, int);
 static int gz_zero(gz_statep, z_off64_t);
 
 /* Initialize state for writing a gzip file.  Mark initialization by setting
-   state->size to non-zero.  Return -1 on failure or 0 on success. */
+   state->size to non-zero.  Return -1 on a memory allocation failure, or 0 on
+   success. */
 static int gz_init(gz_statep state) {
     int ret;
     z_stream *strm = &(state->strm);
@@ -61,11 +62,11 @@ static int gz_init(gz_statep state) {
 }
 
 /* Compress whatever is at avail_in and next_in and write to the output file.
-   Return -1 if there is an error writing to the output file, otherwise 0.
-   flush is assumed to be a valid deflate() flush value.  If flush is Z_FINISH,
-   then the deflate() state is reset to start a new gzip stream.  If gz->direct
-   is true, then simply write to the output file without compressing, and
-   ignore flush. */
+   Return -1 if there is an error writing to the output file or if gz_init()
+   fails to allocate memory, otherwise 0.  flush is assumed to be a valid
+   deflate() flush value.  If flush is Z_FINISH, then the deflate() state is
+   reset to start a new gzip stream.  If gz->direct is true, then simply write
+   to the output file without compressing, and ignore flush. */
 static int gz_comp(gz_statep state, int flush) {
     int ret;
     ssize_t got;
@@ -123,7 +124,8 @@ static int gz_comp(gz_statep state, int flush) {
     return 0;
 }
 
-/* Compress len zeros to output.  Return -1 on error, 0 on success. */
+/* Compress len zeros to output.  Return -1 on a write error or memory
+   allocation failure by gz_comp(), or 0 on success. */
 static int gz_zero(gz_statep state, z_off64_t len) {
     int first;
     unsigned n;
@@ -292,23 +294,23 @@ int ZEXPORTVA gzvprintf(gzFile file, const char *format, va_list va) {
 
     /* get internal structure */
     if (file == NULL)
-        return -1;
+        return Z_STREAM_ERROR;
     state = (gz_statep)file;
     strm = &(state->strm);
 
     /* check that we're writing and that there's no error */
     if (state->mode != GZ_WRITE || state->err != Z_OK)
-        return 0;
+        return Z_STREAM_ERROR;
 
     /* make sure we have some buffer space */
     if (state->size == 0 && gz_init(state) == -1)
-        return 0;
+        return state->err;
 
     /* check for seek request */
     if (state->seek) {
         state->seek = 0;
         if (gz_zero(state, state->skip) == -1)
-            return 0;
+            return state->err;
     }
 
     /* do the printf() into the input buffer, put length in len -- the input
@@ -331,7 +333,7 @@ int ZEXPORTVA gzvprintf(gzFile file, const char *format, va_list va) {
         left = strm->avail_in - state->size;
         strm->avail_in = state->size;
         if (gz_comp(state, Z_NO_FLUSH) == -1)
-            return 0;
+            return state->err;
         memcpy(state->in, state->in + state->size, left);
         strm->next_in = state->in;
         strm->avail_in = left;
@@ -355,7 +357,7 @@ int ZEXPORT gzflush(gzFile file, int flush) {
 
     /* get internal structure */
     if (file == NULL)
-        return -1;
+        return Z_STREAM_ERROR;
     state = (gz_statep)file;
 
     /* check that we're writing and that there's no error */
@@ -370,7 +372,7 @@ int ZEXPORT gzflush(gzFile file, int flush) {
     if (state->seek) {
         state->seek = 0;
         if (gz_zero(state, state->skip) == -1)
-            return -1;
+            return state->err;
     }
 
     /* compress remaining data with requested flush */
@@ -401,7 +403,7 @@ int ZEXPORT gzsetparams(gzFile file, int level, int strategy) {
     if (state->seek) {
         state->seek = 0;
         if (gz_zero(state, state->skip) == -1)
-            return -1;
+            return state->err;
     }
 
     /* change compression parameters for subsequent input */