Add an internal utility function to simplify the many, many places where

the number of bytes read is actually not important as long as we have at
least what we ask for.  Illustrate its benefits by using it throughout
the ZIP support code, except for the few cases where it doesn't apply.

Approved by:	kientzle

3 files changed, 24 insertions, 25 deletions

diff --git a/lib/libarchive/archive_read.c b/lib/libarchive/archive_read.c
index 8ef839a..1028c5d 100644
--- a/lib/libarchive/archive_read.c
+++ b/lib/libarchive/archive_read.c
@@ -741,3 +741,14 @@ __archive_read_register_compression(struct archive_read *a,
 	__archive_errx(1, "Not enough slots for compression registration");
 	return (NULL); /* Never actually executed. */
 }
+
+/* used internally to simplify read-ahead */
+const void *
+__archive_read_ahead(struct archive_read *a, size_t len)
+{
+	const void *h;
+
+	if ((a->decompressor->read_ahead)(a, &h, len) < (ssize_t)len)
+		return (NULL);
+	return (h);
+}
diff --git a/lib/libarchive/archive_read_private.h b/lib/libarchive/archive_read_private.h
index f9b1749..da9cfb5 100644
--- a/lib/libarchive/archive_read_private.h
+++ b/lib/libarchive/archive_read_private.h
@@ -173,4 +173,7 @@ struct decompressor_t
 	    int (*bid)(const void *, size_t),
 	    int (*init)(struct archive_read *, const void *, size_t));
 
+const void
+	*__archive_read_ahead(struct archive_read *, size_t);
+
 #endif
diff --git a/lib/libarchive/archive_read_support_format_zip.c b/lib/libarchive/archive_read_support_format_zip.c
index 52392cc..5e38ea2 100644
--- a/lib/libarchive/archive_read_support_format_zip.c
+++ b/lib/libarchive/archive_read_support_format_zip.c
@@ -166,18 +166,14 @@ archive_read_support_format_zip(struct archive *_a)
 static int
 archive_read_format_zip_bid(struct archive_read *a)
 {
-	int bytes_read;
 	int bid = 0;
-	const void *h;
 	const char *p;
 
 	if (a->archive.archive_format == ARCHIVE_FORMAT_ZIP)
 		bid += 1;
 
-	bytes_read = (a->decompressor->read_ahead)(a, &h, 4);
-	if (bytes_read < 4)
-	    return (-1);
-	p = (const char *)h;
+	if ((p = __archive_read_ahead(a, 4)) == NULL)
+		return (-1);
 
 	/*
 	 * Bid of 30 here is: 16 bits for "PK",
@@ -198,7 +194,6 @@ static int
 archive_read_format_zip_read_header(struct archive_read *a,
     struct archive_entry *entry)
 {
-	int bytes_read;
 	const void *h;
 	const char *signature;
 	struct zip *zip;
@@ -213,8 +208,7 @@ archive_read_format_zip_read_header(struct archive_read *a,
 	zip->end_of_entry_cleanup = 0;
 	zip->entry_uncompressed_bytes_read = 0;
 	zip->entry_compressed_bytes_read = 0;
-	bytes_read = (a->decompressor->read_ahead)(a, &h, 4);
-	if (bytes_read < 4)
+	if ((h = __archive_read_ahead(a, 4)) == NULL)
 		return (ARCHIVE_FATAL);
 
 	signature = (const char *)h;
@@ -261,16 +255,12 @@ zip_read_file_header(struct archive_read *a, struct archive_entry *entry,
 {
 	const struct zip_file_header *p;
 	const void *h;
-	int bytes_read;
 
-	bytes_read =
-	    (a->decompressor->read_ahead)(a, &h, sizeof(struct zip_file_header));
-	if (bytes_read < (int)sizeof(struct zip_file_header)) {
+	if ((p = __archive_read_ahead(a, sizeof *p)) == NULL) {
 		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
 		    "Truncated ZIP file header");
 		return (ARCHIVE_FATAL);
 	}
-	p = (const struct zip_file_header *)h;
 
 	zip->version = p->version[0];
 	zip->system = p->version[1];
@@ -297,15 +287,14 @@ zip_read_file_header(struct archive_read *a, struct archive_entry *entry,
 
 
 	/* Read the filename. */
-	bytes_read = (a->decompressor->read_ahead)(a, &h, zip->filename_length);
-	if (bytes_read < zip->filename_length) {
+	if ((h = __archive_read_ahead(a, zip->filename_length)) == NULL) {
 		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
 		    "Truncated ZIP file header");
 		return (ARCHIVE_FATAL);
 	}
 	if (archive_string_ensure(&zip->pathname, zip->filename_length) == NULL)
 		__archive_errx(1, "Out of memory");
-	archive_strncpy(&zip->pathname, (const char *)h, zip->filename_length);
+	archive_strncpy(&zip->pathname, h, zip->filename_length);
 	(a->decompressor->consume)(a, zip->filename_length);
 	archive_entry_set_pathname(entry, zip->pathname.s);
 
@@ -315,8 +304,7 @@ zip_read_file_header(struct archive_read *a, struct archive_entry *entry,
 		zip->mode = AE_IFREG | 0777;
 
 	/* Read the extra data. */
-	bytes_read = (a->decompressor->read_ahead)(a, &h, zip->extra_length);
-	if (bytes_read < zip->extra_length) {
+	if ((h = __archive_read_ahead(a, zip->extra_length)) == NULL) {
 		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
 		    "Truncated ZIP file header");
 		return (ARCHIVE_FATAL);
@@ -387,21 +375,18 @@ archive_read_format_zip_read_data(struct archive_read *a,
 	if (zip->end_of_entry) {
 		if (!zip->end_of_entry_cleanup) {
 			if (zip->flags & ZIP_LENGTH_AT_END) {
-				const void *h;
 				const char *p;
-				int bytes_read =
-				    (a->decompressor->read_ahead)(a, &h, 16);
-				if (bytes_read < 16) {
+
+				if ((p = __archive_read_ahead(a, 16)) == NULL) {
 					archive_set_error(&a->archive,
 					    ARCHIVE_ERRNO_FILE_FORMAT,
 					    "Truncated ZIP end-of-file record");
 					return (ARCHIVE_FATAL);
 				}
-				p = (const char *)h;
 				zip->crc32 = i4(p + 4);
 				zip->compressed_size = u4(p + 8);
 				zip->uncompressed_size = u4(p + 12);
-				bytes_read = (a->decompressor->consume)(a, 16);
+				(a->decompressor->consume)(a, 16);
 			}
 
 			/* Check file size, CRC against these values. */