libarchive/test/test_write_format_zip_large.c - third_party/libarchive - Git at Google

 /*-
  * Copyright (c) 2003-2007,2013 Tim Kientzle
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #include "test.h"
 __FBSDID("$FreeBSD$");

 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>

 /*
  * This is a somewhat tricky test that verifies the ability to
  * write and read very large entries to zip archives.
  *
  * See test_tar_large.c for more information about the machinery
  * being used here.
  */

 static size_t nullsize;
 static void *nulldata;

 struct fileblock {
 	struct fileblock *next;
 	int	size;
 	void *buff;
 	int64_t gap_size; /* Size of following gap */
 };

 struct fileblocks {
 	int64_t filesize;
 	int64_t fileposition;
 	int64_t gap_remaining;
 	void *buff;
 	struct fileblock *first;
 	struct fileblock *current;
 	struct fileblock *last;
 };

 /* The following size definitions simplify things below. */
 #define KB ((int64_t)1024)
 #define MB ((int64_t)1024 * KB)
 #define GB ((int64_t)1024 * MB)
 #define TB ((int64_t)1024 * GB)

 static int64_t	memory_read_skip(struct archive *, void *, int64_t request);
 static ssize_t	memory_read(struct archive *, void *, const void **buff);
 static ssize_t	memory_write(struct archive *, void *, const void *, size_t);

 static int16_t le16(const void *_p) {
 	const uint8_t *p = _p;
 	return (0xff & (int16_t)p[0]) | ((0xff & (int16_t)p[1]) << 8);
 }

 static int32_t le32(const void *_p) {
 	const uint8_t *p = _p;
 	int32_t v = 0xffff & (int32_t)le16(_p);
 	return v + ((0xffff & (int32_t)le16(p + 2)) << 16);
 }

 static int64_t le64(const void *_p) {
 	const uint8_t *p = _p;
 	int64_t v = 0xffffffff & (int64_t)le32(_p);
 	return v + ((0xffffffff & (int64_t)le32(p + 4)) << 32);
 }

 static ssize_t
 memory_write(struct archive *a, void *_private, const void *buff, size_t size)
 {
 	struct fileblocks *private = _private;
 	struct fileblock *block;

 	(void)a;

 	if ((const char *)nulldata <= (const char *)buff
 	    && (const char *)buff < (const char *)nulldata + nullsize) {
 		/* We don't need to store a block of gap data. */
 		private->last->gap_size += (int64_t)size;
 	} else {
 		/* Yes, we're assuming the very first write is metadata. */
 		/* It's header or metadata, copy and save it. */
 		block = (struct fileblock *)malloc(sizeof(*block));
 		memset(block, 0, sizeof(*block));
 		block->size = (int)size;
 		block->buff = malloc(size);
 		memcpy(block->buff, buff, size);
 		if (private->last == NULL) {
 			private->first = private->last = block;
 		} else {
 			private->last->next = block;
 			private->last = block;
 		}
 		block->next = NULL;
 	}
 	private->filesize += size;
 	return ((long)size);
 }

 static ssize_t
 memory_read(struct archive *a, void *_private, const void **buff)
 {
 	struct fileblocks *private = _private;
 	ssize_t size;

 	(void)a;

 	while (private->current != NULL && private->buff == NULL && private->gap_remaining == 0) {
 		private->current = private->current->next;
 		if (private->current != NULL) {
 			private->buff = private->current->buff;
 			private->gap_remaining = private->current->gap_size;
 		}
 	}

 	if (private->current == NULL)
 		return (0);

 	/* If there's real data, return that. */
 	if (private->buff != NULL) {
 		*buff = private->buff;
 		size = ((char *)private->current->buff + private->current->size)
 		    - (char *)private->buff;
 		private->buff = NULL;
 		private->fileposition += size;
 		return (size);
 	}

 	/* Big gap: too big to return all at once, so just return some. */
 	if (private->gap_remaining > (int64_t)nullsize) {
 		private->gap_remaining -= nullsize;
 		*buff = nulldata;
 		private->fileposition += nullsize;
 		return (nullsize);
 	}

 	/* Small gap: finish the gap and prep for next block. */
 	if (private->gap_remaining > 0) {
 		size = (ssize_t)private->gap_remaining;
 		*buff = nulldata;
 		private->gap_remaining = 0;
 		private->fileposition += size;

 		private->current = private->current->next;
 		if (private->current != NULL) {
 			private->buff = private->current->buff;
 			private->gap_remaining = private->current->gap_size;
 		}

 		return (size);
 	}
 	fprintf(stderr, "\n\n\nInternal failure\n\n\n");
 	exit(1);
 }

 static int
 memory_read_open(struct archive *a, void *_private)
 {
 	struct fileblocks *private = _private;

 	(void)a; /* UNUSED */

 	private->current = private->first;
 	private->fileposition = 0;
 	if (private->current != NULL) {
 		private->buff = private->current->buff;
 		private->gap_remaining = private->current->gap_size;
 	}
 	return (ARCHIVE_OK);
 }

 static int64_t
 memory_read_seek(struct archive *a, void *_private, int64_t offset, int whence)
 {
 	struct fileblocks *private = _private;

 	(void)a;
 	if (whence == SEEK_END) {
 		offset = private->filesize + offset;
 	} else if (whence == SEEK_CUR) {
 		offset = private->fileposition + offset;
 	}

 	if (offset < 0) {
 		fprintf(stderr, "\n\n\nInternal failure: negative seek\n\n\n");
 		exit(1);
 	}

 	/* We've converted the request into a SEEK_SET. */
 	private->fileposition = offset;

 	/* Walk the block list to find the new position. */
 	offset = 0;
 	private->current = private->first;
 	while (private->current != NULL) {
 		if (offset + private->current->size > private->fileposition) {
 			/* Position is in this block. */
 			private->buff = (char *)private->current->buff
 			    + private->fileposition - offset;
 			private->gap_remaining = private->current->gap_size;
 			return private->fileposition;
 		}
 		offset += private->current->size;
 		if (offset + private->current->gap_size > private->fileposition) {
 			/* Position is in this gap. */
 			private->buff = NULL;
 			private->gap_remaining = private->current->gap_size
 			    - (private->fileposition - offset);
 			return private->fileposition;
 		}
 		offset += private->current->gap_size;
 		/* Skip to next block. */
 		private->current = private->current->next;
 	}
 	if (private->fileposition == private->filesize) {
 		return private->fileposition;
 	}
 	fprintf(stderr, "\n\n\nInternal failure: over-sized seek\n\n\n");
 	exit(1);
 }

 static int64_t
 memory_read_skip(struct archive *a, void *_private, int64_t skip)
 {
 	struct fileblocks *private = _private;
 	int64_t old_position = private->fileposition;
 	int64_t new_position = memory_read_seek(a, _private, skip, SEEK_CUR);
 	return (new_position - old_position);
 }

 static struct fileblocks *
 fileblocks_new(void)
 {
 	struct fileblocks *fileblocks;

 	fileblocks = calloc(1, sizeof(struct fileblocks));
 	return fileblocks;
 }

 static void
 fileblocks_free(struct fileblocks *fileblocks)
 {
 	while (fileblocks->first != NULL) {
 		struct fileblock *b = fileblocks->first;
 		fileblocks->first = fileblocks->first->next;
 		free(b->buff);
 		free(b);
 	}
 	free(fileblocks);
 }


 /* The sizes of the entries we're going to generate. */
 static int64_t test_sizes[] = {
 	/* Test for 32-bit signed overflow. */
 	2 * GB - 1, 2 * GB, 2 * GB + 1,
 	/* Test for 32-bit unsigned overflow. */
 	4 * GB - 1, 4 * GB, 4 * GB + 1,
 	/* And beyond ... because we can. */
 	16 * GB - 1, 16 * GB, 16 * GB + 1,
 	64 * GB - 1, 64 * GB, 64 * GB + 1,
 	256 * GB - 1, 256 * GB, 256 * GB + 1,
 	1 * TB,
 	0
 };


 static void
 verify_large_zip(struct archive *a, struct fileblocks *fileblocks)
 {
 	char namebuff[64];
 	struct archive_entry *ae;
 	int i;

 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_set_options(a, "zip:ignorecrc32"));
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_set_open_callback(a, memory_read_open));
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_set_read_callback(a, memory_read));
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_set_skip_callback(a, memory_read_skip));
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_set_seek_callback(a, memory_read_seek));
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_set_callback_data(a, fileblocks));
 	assertEqualIntA(a, ARCHIVE_OK, archive_read_open1(a));

 	/*
 	 * Read entries back.
 	 */
 	for (i = 0; test_sizes[i] > 0; i++) {
 		assertEqualIntA(a, ARCHIVE_OK,
 		    archive_read_next_header(a, &ae));
 		sprintf(namebuff, "file_%d", i);
 		assertEqualString(namebuff, archive_entry_pathname(ae));
 		assertEqualInt(test_sizes[i], archive_entry_size(ae));
 	}
 	assertEqualIntA(a, 0, archive_read_next_header(a, &ae));
 	assertEqualString("lastfile", archive_entry_pathname(ae));

 	assertEqualIntA(a, ARCHIVE_EOF, archive_read_next_header(a, &ae));

 	/* Close out the archive. */
 	assertEqualIntA(a, ARCHIVE_OK, archive_read_close(a));
 }

 DEFINE_TEST(test_write_format_zip_large)
 {
 	int i;
 	char namebuff[64];
 	struct fileblocks *fileblocks = fileblocks_new();
 	struct archive_entry *ae;
 	struct archive *a;
 	const char *p;
 	const char *cd_start, *zip64_eocd, *zip64_locator, *eocd;
 	int64_t cd_size;
 	char *buff;
 	int64_t  filesize;
 	size_t writesize, buffsize, s;

 	nullsize = (size_t)(1 * MB);
 	nulldata = malloc(nullsize);
 	memset(nulldata, 0xAA, nullsize);

 	/*
 	 * Open an archive for writing.
 	 */
 	a = archive_write_new();
 	archive_write_set_format_zip(a);
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_write_set_options(a, "zip:compression=store"));
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_write_set_options(a, "zip:fakecrc32"));
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_write_set_bytes_per_block(a, 0)); /* No buffering. */
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_write_open(a, fileblocks, NULL, memory_write, NULL));

 	/*
 	 * Write a series of large files to it.
 	 */
 	for (i = 0; test_sizes[i] != 0; i++) {
 		assert((ae = archive_entry_new()) != NULL);
 		sprintf(namebuff, "file_%d", i);
 		archive_entry_copy_pathname(ae, namebuff);
 		archive_entry_set_mode(ae, S_IFREG | 0755);
 		filesize = test_sizes[i];
 		archive_entry_set_size(ae, filesize);

 		assertEqualIntA(a, ARCHIVE_OK,
 		    archive_write_header(a, ae));
 		archive_entry_free(ae);

 		/*
 		 * Write the actual data to the archive.
 		 */
 		while (filesize > 0) {
 			writesize = nullsize;
 			if ((int64_t)writesize > filesize)
 				writesize = (size_t)filesize;
 			assertEqualIntA(a, (int)writesize,
 			    (int)archive_write_data(a, nulldata, writesize));
 			filesize -= writesize;
 		}
 	}

 	assert((ae = archive_entry_new()) != NULL);
 	archive_entry_copy_pathname(ae, "lastfile");
 	archive_entry_set_mode(ae, S_IFREG | 0755);
 	assertA(0 == archive_write_header(a, ae));
 	archive_entry_free(ae);

 	/* Close out the archive. */
 	assertEqualIntA(a, ARCHIVE_OK, archive_write_close(a));
 	assertEqualInt(ARCHIVE_OK, archive_write_free(a));

 	/*
 	 * Read back with seeking reader:
 	 */
 	a = archive_read_new();
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_support_format_zip_seekable(a));
 	verify_large_zip(a, fileblocks);
 	assertEqualInt(ARCHIVE_OK, archive_read_free(a));

 	/*
 	 * Read back with streaming reader:
 	 */
 	a = archive_read_new();
 	assertEqualIntA(a, ARCHIVE_OK,
 	    archive_read_support_format_zip_streamable(a));
 	verify_large_zip(a, fileblocks);
 	assertEqualInt(ARCHIVE_OK, archive_read_free(a));

 	/*
 	 * Manually verify some of the final bytes of the archives.
 	 */
 	/* Collect the final bytes together */
 #define FINAL_SIZE 8192
 	buff = malloc(FINAL_SIZE);
 	buffsize = 0;
 	memory_read_open(NULL, fileblocks);
 	memory_read_seek(NULL, fileblocks, -FINAL_SIZE, SEEK_END);
 	while ((s = memory_read(NULL, fileblocks, (const void **)&p)) > 0) {
 		memcpy(buff + buffsize, p, s);
 		buffsize += s;
 	}
 	assertEqualInt(buffsize, FINAL_SIZE);

 	p = buff + buffsize;

 	/* Verify regular end-of-central-directory record */
 	eocd = p - 22;
 	assertEqualMem(eocd, "PK\005\006\0\0\0\0", 8);
 	assertEqualMem(eocd + 8, "\021\0\021\0", 4); /* 17 entries total */
 	cd_size = le32(eocd + 12);
 	/* Start of CD offset should be 0xffffffff */
 	assertEqualMem(eocd + 16, "\xff\xff\xff\xff", 4);
 	assertEqualMem(eocd + 20, "\0\0", 2);	/* No Zip comment */

 	/* Verify Zip64 locator */
 	zip64_locator = p - 42;
 	assertEqualMem(zip64_locator, "PK\006\007\0\0\0\0", 8);
 	zip64_eocd = p - (fileblocks->filesize - le64(zip64_locator + 8));
 	assertEqualMem(zip64_locator + 16, "\001\0\0\0", 4);

 	/* Verify Zip64 end-of-cd record. */
 	assert(zip64_eocd == p - 98);
 	assertEqualMem(zip64_eocd, "PK\006\006", 4);
 	assertEqualInt(44, le64(zip64_eocd + 4)); // Size of EoCD record - 12
 	assertEqualMem(zip64_eocd + 12, "\055\0", 2);  // Made by version: 45
 	assertEqualMem(zip64_eocd + 14, "\055\0", 2);  // Requires version: 45
 	assertEqualMem(zip64_eocd + 16, "\0\0\0\0", 4); // This disk
 	assertEqualMem(zip64_eocd + 20, "\0\0\0\0", 4); // Total disks
 	assertEqualInt(17, le64(zip64_eocd + 24));  // Entries on this disk
 	assertEqualInt(17, le64(zip64_eocd + 32));  // Total entries
 	cd_size = le64(zip64_eocd + 40);
 	cd_start = p - (fileblocks->filesize - le64(zip64_eocd + 48));

 	assert(cd_start + cd_size == zip64_eocd);

 	assertEqualInt(le64(zip64_eocd + 48) // Start of CD
 	    + cd_size
 	    + 56 // Size of Zip64 EOCD
 	    + 20 // Size of Zip64 locator
 	    + 22, // Size of EOCD
 	    fileblocks->filesize);

 	// TODO: Scan entire Central Directory, sanity-check all data
 	assertEqualMem(cd_start, "PK\001\002", 4);

 	fileblocks_free(fileblocks);
 	free(buff);
 	free(nulldata);
 }
	/*-
	* Copyright (c) 2003-2007,2013 Tim Kientzle
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/
	#include "test.h"
	__FBSDID("$FreeBSD$");

	#include <errno.h>
	#include <stdlib.h>
	#include <string.h>

	/*
	* This is a somewhat tricky test that verifies the ability to
	* write and read very large entries to zip archives.
	*
	* See test_tar_large.c for more information about the machinery
	* being used here.
	*/

	static size_t nullsize;
	static void *nulldata;

	struct fileblock {
	struct fileblock *next;
	int size;
	void *buff;
	int64_t gap_size; /* Size of following gap */
	};

	struct fileblocks {
	int64_t filesize;
	int64_t fileposition;
	int64_t gap_remaining;
	void *buff;
	struct fileblock *first;
	struct fileblock *current;
	struct fileblock *last;
	};

	/* The following size definitions simplify things below. */
	#define KB ((int64_t)1024)
	#define MB ((int64_t)1024 * KB)
	#define GB ((int64_t)1024 * MB)
	#define TB ((int64_t)1024 * GB)

	static int64_t memory_read_skip(struct archive , void , int64_t request);
	static ssize_t memory_read(struct archive , void , const void **buff);
	static ssize_t memory_write(struct archive , void , const void *, size_t);

	static int16_t le16(const void *_p) {
	const uint8_t *p = _p;
	return (0xff & (int16_t)p[0]) \| ((0xff & (int16_t)p[1]) << 8);
	}

	static int32_t le32(const void *_p) {
	const uint8_t *p = _p;
	int32_t v = 0xffff & (int32_t)le16(_p);
	return v + ((0xffff & (int32_t)le16(p + 2)) << 16);
	}

	static int64_t le64(const void *_p) {
	const uint8_t *p = _p;
	int64_t v = 0xffffffff & (int64_t)le32(_p);
	return v + ((0xffffffff & (int64_t)le32(p + 4)) << 32);
	}

	static ssize_t
	memory_write(struct archive a, void _private, const void *buff, size_t size)
	{
	struct fileblocks *private = _private;
	struct fileblock *block;

	(void)a;

	if ((const char )nulldata <= (const char )buff
	&& (const char )buff < (const char )nulldata + nullsize) {
	/* We don't need to store a block of gap data. */
	private->last->gap_size += (int64_t)size;
	} else {
	/* Yes, we're assuming the very first write is metadata. */
	/* It's header or metadata, copy and save it. */
	block = (struct fileblock )malloc(sizeof(block));
	memset(block, 0, sizeof(*block));
	block->size = (int)size;
	block->buff = malloc(size);
	memcpy(block->buff, buff, size);
	if (private->last == NULL) {
	private->first = private->last = block;
	} else {
	private->last->next = block;
	private->last = block;
	}
	block->next = NULL;
	}
	private->filesize += size;
	return ((long)size);
	}

	static ssize_t
	memory_read(struct archive a, void _private, const void **buff)
	{
	struct fileblocks *private = _private;
	ssize_t size;

	(void)a;

	while (private->current != NULL && private->buff == NULL && private->gap_remaining == 0) {
	private->current = private->current->next;
	if (private->current != NULL) {
	private->buff = private->current->buff;
	private->gap_remaining = private->current->gap_size;
	}
	}

	if (private->current == NULL)
	return (0);

	/* If there's real data, return that. */
	if (private->buff != NULL) {
	*buff = private->buff;
	size = ((char *)private->current->buff + private->current->size)
	- (char *)private->buff;
	private->buff = NULL;
	private->fileposition += size;
	return (size);
	}

	/* Big gap: too big to return all at once, so just return some. */
	if (private->gap_remaining > (int64_t)nullsize) {
	private->gap_remaining -= nullsize;
	*buff = nulldata;
	private->fileposition += nullsize;
	return (nullsize);
	}

	/* Small gap: finish the gap and prep for next block. */
	if (private->gap_remaining > 0) {
	size = (ssize_t)private->gap_remaining;
	*buff = nulldata;
	private->gap_remaining = 0;
	private->fileposition += size;

	private->current = private->current->next;
	if (private->current != NULL) {
	private->buff = private->current->buff;
	private->gap_remaining = private->current->gap_size;
	}

	return (size);
	}
	fprintf(stderr, "\n\n\nInternal failure\n\n\n");
	exit(1);
	}

	static int
	memory_read_open(struct archive a, void _private)
	{
	struct fileblocks *private = _private;

	(void)a; /* UNUSED */

	private->current = private->first;
	private->fileposition = 0;
	if (private->current != NULL) {
	private->buff = private->current->buff;
	private->gap_remaining = private->current->gap_size;
	}
	return (ARCHIVE_OK);
	}

	static int64_t
	memory_read_seek(struct archive a, void _private, int64_t offset, int whence)
	{
	struct fileblocks *private = _private;

	(void)a;
	if (whence == SEEK_END) {
	offset = private->filesize + offset;
	} else if (whence == SEEK_CUR) {
	offset = private->fileposition + offset;
	}

	if (offset < 0) {
	fprintf(stderr, "\n\n\nInternal failure: negative seek\n\n\n");
	exit(1);
	}

	/* We've converted the request into a SEEK_SET. */
	private->fileposition = offset;

	/* Walk the block list to find the new position. */
	offset = 0;
	private->current = private->first;
	while (private->current != NULL) {
	if (offset + private->current->size > private->fileposition) {
	/* Position is in this block. */
	private->buff = (char *)private->current->buff
	+ private->fileposition - offset;
	private->gap_remaining = private->current->gap_size;
	return private->fileposition;
	}
	offset += private->current->size;
	if (offset + private->current->gap_size > private->fileposition) {
	/* Position is in this gap. */
	private->buff = NULL;
	private->gap_remaining = private->current->gap_size
	- (private->fileposition - offset);
	return private->fileposition;
	}
	offset += private->current->gap_size;
	/* Skip to next block. */
	private->current = private->current->next;
	}
	if (private->fileposition == private->filesize) {
	return private->fileposition;
	}
	fprintf(stderr, "\n\n\nInternal failure: over-sized seek\n\n\n");
	exit(1);
	}

	static int64_t
	memory_read_skip(struct archive a, void _private, int64_t skip)
	{
	struct fileblocks *private = _private;
	int64_t old_position = private->fileposition;
	int64_t new_position = memory_read_seek(a, _private, skip, SEEK_CUR);
	return (new_position - old_position);
	}

	static struct fileblocks *
	fileblocks_new(void)
	{
	struct fileblocks *fileblocks;

	fileblocks = calloc(1, sizeof(struct fileblocks));
	return fileblocks;
	}

	static void
	fileblocks_free(struct fileblocks *fileblocks)
	{
	while (fileblocks->first != NULL) {
	struct fileblock *b = fileblocks->first;
	fileblocks->first = fileblocks->first->next;
	free(b->buff);
	free(b);
	}
	free(fileblocks);
	}


	/* The sizes of the entries we're going to generate. */
	static int64_t test_sizes[] = {
	/* Test for 32-bit signed overflow. */
	2 * GB - 1, 2 * GB, 2 * GB + 1,
	/* Test for 32-bit unsigned overflow. */
	4 * GB - 1, 4 * GB, 4 * GB + 1,
	/* And beyond ... because we can. */
	16 * GB - 1, 16 * GB, 16 * GB + 1,
	64 * GB - 1, 64 * GB, 64 * GB + 1,
	256 * GB - 1, 256 * GB, 256 * GB + 1,
	1 * TB,
	0
	};


	static void
	verify_large_zip(struct archive a, struct fileblocks fileblocks)
	{
	char namebuff[64];
	struct archive_entry *ae;
	int i;

	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_set_options(a, "zip:ignorecrc32"));
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_set_open_callback(a, memory_read_open));
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_set_read_callback(a, memory_read));
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_set_skip_callback(a, memory_read_skip));
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_set_seek_callback(a, memory_read_seek));
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_set_callback_data(a, fileblocks));
	assertEqualIntA(a, ARCHIVE_OK, archive_read_open1(a));

	/*
	* Read entries back.
	*/
	for (i = 0; test_sizes[i] > 0; i++) {
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_next_header(a, &ae));
	sprintf(namebuff, "file_%d", i);
	assertEqualString(namebuff, archive_entry_pathname(ae));
	assertEqualInt(test_sizes[i], archive_entry_size(ae));
	}
	assertEqualIntA(a, 0, archive_read_next_header(a, &ae));
	assertEqualString("lastfile", archive_entry_pathname(ae));

	assertEqualIntA(a, ARCHIVE_EOF, archive_read_next_header(a, &ae));

	/* Close out the archive. */
	assertEqualIntA(a, ARCHIVE_OK, archive_read_close(a));
	}

	DEFINE_TEST(test_write_format_zip_large)
	{
	int i;
	char namebuff[64];
	struct fileblocks *fileblocks = fileblocks_new();
	struct archive_entry *ae;
	struct archive *a;
	const char *p;
	const char cd_start, zip64_eocd, zip64_locator, eocd;
	int64_t cd_size;
	char *buff;
	int64_t filesize;
	size_t writesize, buffsize, s;

	nullsize = (size_t)(1 * MB);
	nulldata = malloc(nullsize);
	memset(nulldata, 0xAA, nullsize);

	/*
	* Open an archive for writing.
	*/
	a = archive_write_new();
	archive_write_set_format_zip(a);
	assertEqualIntA(a, ARCHIVE_OK,
	archive_write_set_options(a, "zip:compression=store"));
	assertEqualIntA(a, ARCHIVE_OK,
	archive_write_set_options(a, "zip:fakecrc32"));
	assertEqualIntA(a, ARCHIVE_OK,
	archive_write_set_bytes_per_block(a, 0)); /* No buffering. */
	assertEqualIntA(a, ARCHIVE_OK,
	archive_write_open(a, fileblocks, NULL, memory_write, NULL));

	/*
	* Write a series of large files to it.
	*/
	for (i = 0; test_sizes[i] != 0; i++) {
	assert((ae = archive_entry_new()) != NULL);
	sprintf(namebuff, "file_%d", i);
	archive_entry_copy_pathname(ae, namebuff);
	archive_entry_set_mode(ae, S_IFREG \| 0755);
	filesize = test_sizes[i];
	archive_entry_set_size(ae, filesize);

	assertEqualIntA(a, ARCHIVE_OK,
	archive_write_header(a, ae));
	archive_entry_free(ae);

	/*
	* Write the actual data to the archive.
	*/
	while (filesize > 0) {
	writesize = nullsize;
	if ((int64_t)writesize > filesize)
	writesize = (size_t)filesize;
	assertEqualIntA(a, (int)writesize,
	(int)archive_write_data(a, nulldata, writesize));
	filesize -= writesize;
	}
	}

	assert((ae = archive_entry_new()) != NULL);
	archive_entry_copy_pathname(ae, "lastfile");
	archive_entry_set_mode(ae, S_IFREG \| 0755);
	assertA(0 == archive_write_header(a, ae));
	archive_entry_free(ae);

	/* Close out the archive. */
	assertEqualIntA(a, ARCHIVE_OK, archive_write_close(a));
	assertEqualInt(ARCHIVE_OK, archive_write_free(a));

	/*
	* Read back with seeking reader:
	*/
	a = archive_read_new();
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_support_format_zip_seekable(a));
	verify_large_zip(a, fileblocks);
	assertEqualInt(ARCHIVE_OK, archive_read_free(a));

	/*
	* Read back with streaming reader:
	*/
	a = archive_read_new();
	assertEqualIntA(a, ARCHIVE_OK,
	archive_read_support_format_zip_streamable(a));
	verify_large_zip(a, fileblocks);
	assertEqualInt(ARCHIVE_OK, archive_read_free(a));

	/*
	* Manually verify some of the final bytes of the archives.
	*/
	/* Collect the final bytes together */
	#define FINAL_SIZE 8192
	buff = malloc(FINAL_SIZE);
	buffsize = 0;
	memory_read_open(NULL, fileblocks);
	memory_read_seek(NULL, fileblocks, -FINAL_SIZE, SEEK_END);
	while ((s = memory_read(NULL, fileblocks, (const void **)&p)) > 0) {
	memcpy(buff + buffsize, p, s);
	buffsize += s;
	}
	assertEqualInt(buffsize, FINAL_SIZE);

	p = buff + buffsize;

	/* Verify regular end-of-central-directory record */
	eocd = p - 22;
	assertEqualMem(eocd, "PK\005\006\0\0\0\0", 8);
	assertEqualMem(eocd + 8, "\021\0\021\0", 4); /* 17 entries total */
	cd_size = le32(eocd + 12);
	/* Start of CD offset should be 0xffffffff */
	assertEqualMem(eocd + 16, "\xff\xff\xff\xff", 4);
	assertEqualMem(eocd + 20, "\0\0", 2); /* No Zip comment */

	/* Verify Zip64 locator */
	zip64_locator = p - 42;
	assertEqualMem(zip64_locator, "PK\006\007\0\0\0\0", 8);
	zip64_eocd = p - (fileblocks->filesize - le64(zip64_locator + 8));
	assertEqualMem(zip64_locator + 16, "\001\0\0\0", 4);

	/* Verify Zip64 end-of-cd record. */
	assert(zip64_eocd == p - 98);
	assertEqualMem(zip64_eocd, "PK\006\006", 4);
	assertEqualInt(44, le64(zip64_eocd + 4)); // Size of EoCD record - 12
	assertEqualMem(zip64_eocd + 12, "\055\0", 2); // Made by version: 45
	assertEqualMem(zip64_eocd + 14, "\055\0", 2); // Requires version: 45
	assertEqualMem(zip64_eocd + 16, "\0\0\0\0", 4); // This disk
	assertEqualMem(zip64_eocd + 20, "\0\0\0\0", 4); // Total disks
	assertEqualInt(17, le64(zip64_eocd + 24)); // Entries on this disk
	assertEqualInt(17, le64(zip64_eocd + 32)); // Total entries
	cd_size = le64(zip64_eocd + 40);
	cd_start = p - (fileblocks->filesize - le64(zip64_eocd + 48));

	assert(cd_start + cd_size == zip64_eocd);

	assertEqualInt(le64(zip64_eocd + 48) // Start of CD
	+ cd_size
	+ 56 // Size of Zip64 EOCD
	+ 20 // Size of Zip64 locator
	+ 22, // Size of EOCD
	fileblocks->filesize);

	// TODO: Scan entire Central Directory, sanity-check all data
	assertEqualMem(cd_start, "PK\001\002", 4);

	fileblocks_free(fileblocks);
	free(buff);
	free(nulldata);
	}