1 files changed, 64 insertions, 18 deletions

diff --git a/libarchive/archive_read_data_into_fd.c b/libarchive/archive_read_data_into_fd.c
index 3aeef3b..14f9410 100644
--- a/libarchive/archive_read_data_into_fd.c
+++ b/libarchive/archive_read_data_into_fd.c
@@ -45,31 +45,68 @@ __FBSDID("$FreeBSD: src/lib/libarchive/archive_read_data_into_fd.c,v 1.16 2008/0
 /*
  * This implementation minimizes copying of data and is sparse-file aware.
  */
+static int
+pad_to(struct archive *a, int fd, int can_lseek,
+    size_t nulls_size, const char *nulls,
+    int64_t target_offset, int64_t actual_offset)
+{
+	size_t to_write;
+	ssize_t bytes_written;
+
+	if (can_lseek) {
+		actual_offset = lseek(fd,
+		    target_offset - actual_offset, SEEK_CUR);
+		if (actual_offset != target_offset) {
+			archive_set_error(a, errno, "Seek error");
+			return (ARCHIVE_FATAL);
+		}
+		return (ARCHIVE_OK);
+	}
+	while (target_offset > actual_offset) {
+		to_write = nulls_size;
+		if (target_offset < actual_offset + nulls_size)
+			to_write = (size_t)(target_offset - actual_offset);
+		bytes_written = write(fd, nulls, to_write);
+		if (bytes_written < 0) {
+			archive_set_error(a, errno, "Write error");
+			return (ARCHIVE_FATAL);
+		}
+		actual_offset += bytes_written;
+	}
+	return (ARCHIVE_OK);
+}
+
+
 int
 archive_read_data_into_fd(struct archive *a, int fd)
 {
-	int r;
+	struct stat st;
+	int r, r2;
 	const void *buff;
 	size_t size, bytes_to_write;
-	ssize_t bytes_written, total_written;
-	off_t offset;
-	off_t output_offset;
+	ssize_t bytes_written;
+	int64_t target_offset;
+	int64_t actual_offset = 0;
+	int can_lseek;
+	char *nulls = NULL;
+	size_t nulls_size = 16384;
 
-	__archive_check_magic(a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_DATA, "archive_read_data_into_fd");
+	archive_check_magic(a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_DATA,
+	    "archive_read_data_into_fd");
 
-	total_written = 0;
-	output_offset = 0;
+	can_lseek = (fstat(fd, &st) == 0) && S_ISREG(st.st_mode);
+	if (!can_lseek)
+		nulls = calloc(1, nulls_size);
 
-	while ((r = archive_read_data_block(a, &buff, &size, &offset)) ==
+	while ((r = archive_read_data_block(a, &buff, &size, &target_offset)) ==
 	    ARCHIVE_OK) {
 		const char *p = buff;
-		if (offset > output_offset) {
-			output_offset = lseek(fd,
-			    offset - output_offset, SEEK_CUR);
-			if (output_offset != offset) {
-				archive_set_error(a, errno, "Seek error");
-				return (ARCHIVE_FATAL);
-			}
+		if (target_offset > actual_offset) {
+			r = pad_to(a, fd, can_lseek, nulls_size, nulls,
+			    target_offset, actual_offset);
+			if (r != ARCHIVE_OK)
+				break;
+			actual_offset = target_offset;
 		}
 		while (size > 0) {
 			bytes_to_write = size;
@@ -78,15 +115,24 @@ archive_read_data_into_fd(struct archive *a, int fd)
 			bytes_written = write(fd, p, bytes_to_write);
 			if (bytes_written < 0) {
 				archive_set_error(a, errno, "Write error");
-				return (ARCHIVE_FATAL);
+				r = ARCHIVE_FATAL;
+				goto cleanup;
 			}
-			output_offset += bytes_written;
-			total_written += bytes_written;
+			actual_offset += bytes_written;
 			p += bytes_written;
 			size -= bytes_written;
 		}
 	}
 
+	if (r == ARCHIVE_EOF && target_offset > actual_offset) {
+		r2 = pad_to(a, fd, can_lseek, nulls_size, nulls,
+		    target_offset, actual_offset);
+		if (r2 != ARCHIVE_OK)
+			r = r2;
+	}
+
+cleanup:
+	free(nulls);
 	if (r != ARCHIVE_EOF)
 		return (r);
 	return (ARCHIVE_OK);