file_iterator: use static buffer for zero pages.

include/sqsh_archive_private.h

@@ -227,7 +227,6 @@ struct SqshArchive {
 	uint8_t initialized;
 	struct SqshConfig config;
 	sqsh_mutex_t lock;
-	uint8_t *zero_block;
 };
 
 /**
@@ -275,17 +274,6 @@ int sqsh__archive_metablock_extract_manager(
 		struct SqshArchive *archive,
 		struct SqshExtractManager **metablock_extract_manager);
 
-/**
- * @internal
- * @memberof SqshArchive
- *
- * @brief sqsh__archive_id_table retrieves a zero block.
- *
- * @param archive the SqshArchive to retrieve the zero block from.
- * @return the zero block.
- */
-const uint8_t *sqsh__archive_zero_block(const struct SqshArchive *archive);
-
 /**
  * @internal
  * @memberof SqshArchive

lib/archive/archive.c

@@ -119,13 +119,6 @@ sqsh__archive_init(
 		goto out;
 	}
 
-	archive->zero_block = calloc(
-			sqsh_superblock_block_size(&archive->superblock), sizeof(uint8_t));
-	if (archive->zero_block == NULL) {
-		rv = -SQSH_ERROR_MALLOC_FAILED;
-		goto out;
-	}
-
 	enum SqshSuperblockCompressionId compression_id =
 			sqsh_superblock_compression_id(&archive->superblock);
 	uint32_t data_block_size = sqsh_superblock_block_size(&archive->superblock);
@@ -372,11 +365,6 @@ sqsh_archive_xattr_table(
 	return rv;
 }
 
-const uint8_t *
-sqsh__archive_zero_block(const struct SqshArchive *archive) {
-	return archive->zero_block;
-}
-
 struct SqshMapManager *
 sqsh_archive_map_manager(struct SqshArchive *archive) {
 	return &archive->map_manager;
@@ -412,8 +400,6 @@ sqsh__archive_cleanup(struct SqshArchive *archive) {
 	sqsh__superblock_cleanup(&archive->superblock);
 	sqsh__map_manager_cleanup(&archive->map_manager);
 
-	free(archive->zero_block);
-
 	sqsh_mutex_destroy(&archive->lock);
 
 	return rv;

lib/file/file_iterator.c

@@ -43,6 +43,8 @@
 
 #define BLOCK_INDEX_FINISHED UINT32_MAX
 
+static const uint8_t ZERO_BLOCK[16384] = {0};
+
 int
 sqsh__file_iterator_init(
 		struct SqshFileIterator *iterator, const struct SqshInode *inode) {
@@ -183,8 +185,6 @@ map_block_uncompressed(
 static int
 map_zero_block(struct SqshFileIterator *iterator) {
 	const struct SqshInode *inode = iterator->inode;
-	struct SqshArchive *archive = inode->archive;
-	const uint8_t *zero_block = sqsh__archive_zero_block(archive);
 
 	const sqsh_index_t block_index = iterator->block_index;
 	const bool has_fragment = sqsh_inode_file_has_fragment(inode);
@@ -196,7 +196,8 @@ map_zero_block(struct SqshFileIterator *iterator) {
 	if (file_size == 0) {
 		size = 0;
 	} else if (sparse_size > 0) {
-		size = sparse_size;
+		size = SQSH_MIN(sizeof(ZERO_BLOCK), sparse_size);
+		iterator->sparse_size -= size;
 	} else if (has_fragment || block_index != block_count - 1) {
 		size = iterator->block_size;
 	} else {
@@ -207,8 +208,7 @@ map_zero_block(struct SqshFileIterator *iterator) {
 	}
 
 	iterator->size = size;
-	iterator->data = zero_block;
-	iterator->sparse_size = 0;
+	iterator->data = ZERO_BLOCK;
 
 	return size;
 }

test/file/file_iterator.c

@@ -40,6 +40,9 @@
 #include "../../include/sqsh_inode_private.h"
 #include "../../lib/utils/utils.h"
 
+static const size_t BLOCK_SIZE = 32768;
+static const size_t ZERO_PAGE_SIZE = 16384;
+
 static void
 load_segment_from_compressed_data_block(void) {
 	int rv;
@@ -105,7 +108,7 @@ load_two_segments_from_uncompressed_data_block(void) {
 			/* inode */
 			[INODE_TABLE_OFFSET] = METABLOCK_HEADER(0, 128),
 			INODE_HEADER(2, 0, 0, 0, 0, 1),
-			INODE_BASIC_FILE(8192, 0xFFFFFFFF, 0, 4096 + 5),
+			INODE_BASIC_FILE(8192, 0xFFFFFFFF, 0, BLOCK_SIZE + 5),
 			DATA_BLOCK_REF(1000, 0),
 			DATA_BLOCK_REF(5, 0),
 			/* datablocks */
@@ -140,9 +143,19 @@ load_two_segments_from_uncompressed_data_block(void) {
 	assert(rv > 0);
 
 	size = sqsh_file_iterator_size(&iter);
-	assert(size == 4096 - 1000);
+	assert(size == ZERO_PAGE_SIZE);
 	data = sqsh_file_iterator_data(&iter);
-	for (size_t i = 0; i < size; i++) {
+	for (size_t i = 0; i < ZERO_PAGE_SIZE; i++) {
+		assert(data[i] == 0);
+	}
+
+	rv = sqsh_file_iterator_next(&iter, 1);
+	assert(rv > 0);
+
+	size = sqsh_file_iterator_size(&iter);
+	assert(size == ZERO_PAGE_SIZE - 1000);
+	data = sqsh_file_iterator_data(&iter);
+	for (size_t i = 0; i < ZERO_PAGE_SIZE - 1000; i++) {
 		assert(data[i] == 0);
 	}
 
@@ -237,7 +250,67 @@ load_zero_padding(void) {
 			/* inode */
 			[INODE_TABLE_OFFSET] = METABLOCK_HEADER(0, 128),
 			INODE_HEADER(2, 0, 0, 0, 0, 1),
-			INODE_BASIC_FILE(512, 0xFFFFFFFF, 0, 4096 + 5),
+			INODE_BASIC_FILE(512, 0xFFFFFFFF, 0, BLOCK_SIZE + 5),
+			DATA_BLOCK_REF(0, 1),
+			DATA_BLOCK_REF(0, 1),
+			/* clang-format on */
+	};
+	mk_stub(&archive, payload, sizeof(payload));
+
+	uint64_t inode_ref = sqsh_address_ref_create(0, 0);
+	rv = sqsh__inode_init(&inode, &archive, inode_ref);
+	assert(rv == 0);
+
+	assert(sqsh_inode_type(&inode) == SQSH_INODE_TYPE_FILE);
+	assert(sqsh_inode_file_has_fragment(&inode) == false);
+
+	struct SqshFileIterator iter = {0};
+	rv = sqsh__file_iterator_init(&iter, &inode);
+	assert(rv == 0);
+
+	rv = sqsh_file_iterator_next(&iter, 1);
+	assert(rv > 0);
+
+	size_t size = sqsh_file_iterator_size(&iter);
+	assert(size == BLOCK_SIZE);
+
+	rv = sqsh_file_iterator_next(&iter, 1);
+	assert(rv > 0);
+
+	size = sqsh_file_iterator_size(&iter);
+	assert(size == 5);
+	const uint8_t *data = sqsh_file_iterator_data(&iter);
+	assert(data[0] == 0);
+	assert(data[1] == 0);
+	assert(data[2] == 0);
+	assert(data[3] == 0);
+	assert(data[4] == 0);
+
+	rv = sqsh_file_iterator_next(&iter, 1);
+	assert(rv == 0);
+
+	size = sqsh_file_iterator_size(&iter);
+	assert(size == 0);
+	data = sqsh_file_iterator_data(&iter);
+	assert(data == NULL);
+
+	sqsh__file_iterator_cleanup(&iter);
+	sqsh__inode_cleanup(&inode);
+	sqsh__archive_cleanup(&archive);
+}
+
+static void
+load_zero_big_padding(void) {
+	int rv;
+	struct SqshArchive archive = {0};
+	struct SqshInode inode = {0};
+	uint8_t payload[8192] = {
+			/* clang-format off */
+			SQSH_HEADER,
+			/* inode */
+			[INODE_TABLE_OFFSET] = METABLOCK_HEADER(0, 128),
+			INODE_HEADER(2, 0, 0, 0, 0, 1),
+			INODE_BASIC_FILE(512, 0xFFFFFFFF, 0, BLOCK_SIZE + 5),
 			DATA_BLOCK_REF(0, 1),
 			DATA_BLOCK_REF(0, 1),
 			/* clang-format on */
@@ -259,7 +332,7 @@ load_zero_padding(void) {
 	assert(rv > 0);
 
 	size_t size = sqsh_file_iterator_size(&iter);
-	assert(size == 4096);
+	assert(size == BLOCK_SIZE);
 
 	rv = sqsh_file_iterator_next(&iter, 1);
 	assert(rv > 0);
@@ -291,4 +364,5 @@ TEST(load_two_segments_from_uncompressed_data_block);
 TEST(load_segment_from_uncompressed_data_block);
 TEST(load_segment_from_compressed_data_block);
 TEST(load_zero_padding);
+TEST(load_zero_big_padding);
 DEFINE_END

test/util.c

@@ -24,13 +24,13 @@ mk_stub(struct SqshArchive *sqsh, uint8_t *payload, size_t payload_size) {
 			/* modification_time */
 			UINT32_BYTES(0),
 			/* block_size */
-			UINT32_BYTES(4096),
+			UINT32_BYTES(32768),
 			/* fragment_entry_count */
 			UINT32_BYTES(0),
 			/* compression_id */
 			UINT16_BYTES(SQSH_COMPRESSION_GZIP),
 			/* block_log */
-			UINT16_BYTES(12),
+			UINT16_BYTES(15),
 			/* flags */
 			UINT16_BYTES(0),
 			/* id_count */