Merge remote-tracking branch 'aosp/upstream-master' into 'aosp/master'

am: fa8c3fb3d3

Change-Id: I138b144de30c2c6f80d71b17f2653c084394f891

23 files changed, 565 insertions, 164 deletions

diff --git a/squashfs-tools/Makefile b/squashfs-tools/Makefile
index 52d2582..22fc559 100644
--- a/squashfs-tools/Makefile
+++ b/squashfs-tools/Makefile
@@ -75,6 +75,18 @@ GZIP_SUPPORT = 1
 #LZMA_SUPPORT = 1
 #LZMA_DIR = ../../../../LZMA/lzma465
 
+
+########### Building ZSTD support ############
+#
+# The ZSTD library is supported
+# ZSTD homepage: http://zstd.net
+# ZSTD source repository: https://github.com/facebook/zstd
+#
+# To build using the ZSTD library - install the library and uncomment the
+# ZSTD_SUPPORT line below.
+#
+#ZSTD_SUPPORT = 1
+
 ######## Specifying default compression ########
 #
 # The next line specifies which compression algorithm is used by default
@@ -177,6 +189,14 @@ LIBS += -llz4
 COMPRESSORS += lz4
 endif
 
+ifeq ($(ZSTD_SUPPORT),1)
+CFLAGS += -DZSTD_SUPPORT
+MKSQUASHFS_OBJS += zstd_wrapper.o
+UNSQUASHFS_OBJS += zstd_wrapper.o
+LIBS += -lzstd
+COMPRESSORS += zstd
+endif
+
 ifeq ($(XATTR_SUPPORT),1)
 ifeq ($(XATTR_DEFAULT),1)
 CFLAGS += -DXATTR_SUPPORT -DXATTR_DEFAULT
diff --git a/squashfs-tools/action.c b/squashfs-tools/action.c
index 7e43f17..4b06ccb 100644
--- a/squashfs-tools/action.c
+++ b/squashfs-tools/action.c
@@ -31,7 +31,6 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
-#include <fnmatch.h>
 #include <pwd.h>
 #include <grp.h>
 #include <sys/wait.h>
@@ -39,14 +38,11 @@
 #include <limits.h>
 #include <errno.h>
 
-#ifndef FNM_EXTMATCH /* glibc extension */
-    #define FNM_EXTMATCH 0
-#endif
-
 #include "squashfs_fs.h"
 #include "mksquashfs.h"
 #include "action.h"
 #include "error.h"
+#include "fnmatch_compat.h"
 
 /*
  * code to parse actions
@@ -2288,12 +2284,9 @@ static char *get_start(char *s, int n)
 
 static int subpathname_fn(struct atom *atom, struct action_data *action_data)
 {
-	char *path = strdup(action_data->subpath);
-	int is_match = fnmatch(atom->argv[0], get_start(path,
+	return fnmatch(atom->argv[0], get_start(strdupa(action_data->subpath),
 		count_components(atom->argv[0])),
 		FNM_PATHNAME|FNM_PERIOD|FNM_EXTMATCH) == 0;
-	free(path);
-	return is_match;
 }
 
 /*
diff --git a/squashfs-tools/compressor.c b/squashfs-tools/compressor.c
index 525e316..02b5e90 100644
--- a/squashfs-tools/compressor.c
+++ b/squashfs-tools/compressor.c
@@ -65,6 +65,13 @@ static struct compressor xz_comp_ops = {
 extern struct compressor xz_comp_ops;
 #endif
 
+#ifndef ZSTD_SUPPORT
+static struct compressor zstd_comp_ops = {
+	ZSTD_COMPRESSION, "zstd"
+};
+#else
+extern struct compressor zstd_comp_ops;
+#endif
 
 static struct compressor unknown_comp_ops = {
 	0, "unknown"
@@ -77,6 +84,7 @@ struct compressor *compressor[] = {
 	&lzo_comp_ops,
 	&lz4_comp_ops,
 	&xz_comp_ops,
+	&zstd_comp_ops,
 	&unknown_comp_ops
 };
 
diff --git a/squashfs-tools/fnmatch_compat.h b/squashfs-tools/fnmatch_compat.h
new file mode 100644
index 0000000..7b4afd8
--- /dev/null
+++ b/squashfs-tools/fnmatch_compat.h
@@ -0,0 +1,32 @@
+#ifndef FNMATCH_COMPAT
+#define FNMATCH_COMPAT
+/*
+ * Squashfs
+ *
+ * Copyright (c) 2015
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * fnmatch_compat.h
+ */
+
+#include <fnmatch.h>
+
+#ifndef FNM_EXTMATCH
+#define FNM_EXTMATCH	0
+#endif
+
+#endif
diff --git a/squashfs-tools/gzip_wrapper.c b/squashfs-tools/gzip_wrapper.c
index 076a587..ac32bb9 100644
--- a/squashfs-tools/gzip_wrapper.c
+++ b/squashfs-tools/gzip_wrapper.c
@@ -276,7 +276,7 @@ failed:
 }
 
 
-void gzip_display_options(void *buffer, int size)
+static void gzip_display_options(void *buffer, int size)
 {
 	struct gzip_comp_opts *comp_opts = buffer;
 	int i, printed;
@@ -467,7 +467,7 @@ static int gzip_uncompress(void *d, void *s, int size, int outsize, int *error)
 }
 
 
-void gzip_usage()
+static void gzip_usage()
 {
 	fprintf(stderr, "\t  -Xcompression-level <compression-level>\n");
 	fprintf(stderr, "\t\t<compression-level> should be 1 .. 9 (default "
diff --git a/squashfs-tools/info.c b/squashfs-tools/info.c
index 60a3f5a..7968c77 100644
--- a/squashfs-tools/info.c
+++ b/squashfs-tools/info.c
@@ -134,22 +134,31 @@ void dump_state()
 void *info_thrd(void *arg)
 {
 	sigset_t sigmask;
-	int sig, err, waiting = 0;
+	struct timespec timespec = { .tv_sec = 1, .tv_nsec = 0 };
+	int sig, waiting = 0;
 
 	sigemptyset(&sigmask);
 	sigaddset(&sigmask, SIGQUIT);
 	sigaddset(&sigmask, SIGHUP);
-	sigaddset(&sigmask, SIGALRM);
 
 	while(1) {
-		err = sigwait(&sigmask, &sig);
+		if(waiting)
+			sig = sigtimedwait(&sigmask, NULL, &timespec);
+		else
+			sig = sigwaitinfo(&sigmask, NULL);
 
-		if(err == -1) {
+		if(sig == -1) {
 			switch(errno) {
+			case EAGAIN:
+				/* interval timed out */
+				waiting = 0;
+				/* FALLTHROUGH */
 			case EINTR:
+				/* if waiting, the wait will be longer, but
+				   that's OK */
 				continue;
 			default:
-				BAD_ERROR("sigwait failed "
+				BAD_ERROR("sigtimedwait/sigwaitinfo failed "
 					"because %s\n", strerror(errno));
 			}
 		}
@@ -160,12 +169,8 @@ void *info_thrd(void *arg)
 			/* set one second interval period, if ^\ received
 			   within then, dump queue and cache status */
 			waiting = 1;
-			alarm(1);
-		} else if (sig == SIGQUIT) {
+		} else
 			dump_state();
-		} else if (sig == SIGALRM) {
-			waiting = 0;
-		}
 	}
 }
 
diff --git a/squashfs-tools/lz4_wrapper.c b/squashfs-tools/lz4_wrapper.c
index 3c24971..71b21a8 100644
--- a/squashfs-tools/lz4_wrapper.c
+++ b/squashfs-tools/lz4_wrapper.c
@@ -184,7 +184,7 @@ failed:
 }
 
 
-void lz4_display_options(void *buffer, int size)
+static void lz4_display_options(void *buffer, int size)
 {
 	struct lz4_comp_opts *comp_opts = buffer;
 
@@ -225,11 +225,20 @@ static int lz4_compress(void *strm, void *dest, void *src,  int size,
 {
 	int res;
 
+/* ANDROID CHANGES START*/
+#ifdef ANDROID
 	if(hc)
 		res = LZ4_compress_HC(src, dest, size, block_size,
 				      LZ4HC_CLEVEL_DEFAULT);
 	else
 		res = LZ4_compress_default(src, dest, size, block_size);
+#else
+	if(hc)
+		res = LZ4_compressHC_limitedOutput(src, dest, size, block_size);
+	else
+		res = LZ4_compress_limitedOutput(src, dest, size, block_size);
+#endif
+/* ANDROID CHANGES END */
 
 	if(res == 0) {
 		/*
@@ -262,7 +271,7 @@ static int lz4_uncompress(void *dest, void *src, int size, int outsize,
 }
 
 
-void lz4_usage()
+static void lz4_usage()
 {
 	fprintf(stderr, "\t  -Xhc\n");
 	fprintf(stderr, "\t\tCompress using LZ4 High Compression\n");
diff --git a/squashfs-tools/lzo_wrapper.c b/squashfs-tools/lzo_wrapper.c
index 8c9bf95..f367fad 100644
--- a/squashfs-tools/lzo_wrapper.c
+++ b/squashfs-tools/lzo_wrapper.c
@@ -263,7 +263,7 @@ failed:
 }
 
 
-void lzo_display_options(void *buffer, int size)
+static void lzo_display_options(void *buffer, int size)
 {
 	struct lzo_comp_opts *comp_opts = buffer;
 
@@ -391,7 +391,7 @@ static int lzo_uncompress(void *dest, void *src, int size, int outsize,
 }
 
 
-void lzo_usage()
+static void lzo_usage()
 {
 	int i;
 
diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
index 60be156..cbfc731 100644
--- a/squashfs-tools/mksquashfs.c
+++ b/squashfs-tools/mksquashfs.c
@@ -3,7 +3,7 @@
  * filesystem.
  *
  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,
- * 2012, 2013, 2014
+ * 2012, 2013, 2014, 2017
  * Phillip Lougher <phillip@squashfs.org.uk>
  *
  * This program is free software; you can redistribute it and/or
@@ -46,15 +46,10 @@
 #include <sys/mman.h>
 #include <pthread.h>
 #include <regex.h>
-#include <fnmatch.h>
 #include <sys/wait.h>
 #include <limits.h>
 #include <ctype.h>
 
-#ifndef FNM_EXTMATCH /* glibc extension */
-    #define FNM_EXTMATCH 0
-#endif
-
 #ifndef linux
 #define __BYTE_ORDER BYTE_ORDER
 #define __BIG_ENDIAN BIG_ENDIAN
@@ -97,7 +92,10 @@ FILE *block_map_file = NULL;
 #endif
 /* ANDROID CHANGES END */
 
+#include "fnmatch_compat.h"
+
 int delete = FALSE;
+int quiet = FALSE;
 int fd;
 struct squashfs_super_block sBlk;
 
@@ -118,6 +116,7 @@ int old_exclude = TRUE;
 int use_regex = FALSE;
 int nopad = FALSE;
 int exit_on_error = FALSE;
+static off_t squashfs_start_offset = 0;
 
 long long global_uid = -1, global_gid = -1;
 
@@ -460,8 +459,7 @@ int mangle2(void *strm, char *d, char *s, int size,
 				"code %d\n", comp->name, error);
 	}
 
-	if(c_byte == 0 || c_byte >= size ||
-			(c_byte > (size * ((100.0 - compress_thresh_per) / 100.0)))) {
+	if(c_byte == 0 || c_byte >= size) {
 		memcpy(d, s, size);
 		return size | (data_block ? SQUASHFS_COMPRESSED_BIT_BLOCK :
 			SQUASHFS_COMPRESSED_BIT);
@@ -561,9 +559,9 @@ int read_fs_bytes(int fd, long long byte, int bytes, void *buff)
 
 	pthread_cleanup_push((void *) pthread_mutex_unlock, &pos_mutex);
 	pthread_mutex_lock(&pos_mutex);
-	if(lseek(fd, off, SEEK_SET) == -1) {
+	if(lseek(fd, off+squashfs_start_offset, SEEK_SET) == -1) {
 		ERROR("read_fs_bytes: Lseek on destination failed because %s, "
-			"offset=0x%llx\n", strerror(errno), off);
+			"offset=0x%llx\n", strerror(errno), off+squashfs_start_offset);
 		res = 0;
 	} else if(read_bytes(fd, buff, bytes) < bytes) {
 		ERROR("Read on destination failed\n");
@@ -602,10 +600,10 @@ void write_destination(int fd, long long byte, int bytes, void *buff)
 	pthread_cleanup_push((void *) pthread_mutex_unlock, &pos_mutex);
 	pthread_mutex_lock(&pos_mutex);
 
-	if(lseek(fd, off, SEEK_SET) == -1) {
+	if(lseek(fd, off+squashfs_start_offset, SEEK_SET) == -1) {
 		ERROR("write_destination: Lseek on destination "
 			"failed because %s, offset=0x%llx\n", strerror(errno),
-			off);
+			off+squashfs_start_offset);
 		BAD_ERROR("Probably out of space on output %s\n",
 			block_device ? "block device" : "filesystem");
 	}
@@ -873,13 +871,13 @@ char *subpathname(struct dir_ent *dir_ent)
 }
 
 
-static inline unsigned int get_inode_no(struct inode_info *inode)
+inline unsigned int get_inode_no(struct inode_info *inode)
 {
 	return inode->inode_number;
 }
 
 
-static inline unsigned int get_parent_no(struct dir_info *dir)
+inline unsigned int get_parent_no(struct dir_info *dir)
 {
 	return dir->depth ? get_inode_no(dir->dir_ent->inode) : inode_no;
 }
@@ -1001,10 +999,8 @@ int create_inode(squashfs_inode *i_no, struct dir_info *dir_info,
 			"%d, fragment %d, offset %d, size %d\n", byte_size,
 			start_block, offset, fragment->index, fragment->offset,
 			fragment->size);
-		for(i = 0; i < offset; i++) {
+		for(i = 0; i < offset; i++)
 			TRACE("Block %d, size %d\n", i, block_list[i]);
-			total_size += SQUASHFS_COMPRESSED_SIZE_BLOCK(block_list[i]);
-		}
 /* ANDROID CHANGES START*/
 #ifdef ANDROID
 		sub_path = subpathname(dir_ent);
@@ -1041,10 +1037,8 @@ int create_inode(squashfs_inode *i_no, struct dir_info *dir_info,
 			"blocks %d, fragment %d, offset %d, size %d, nlink %d"
 			"\n", byte_size, start_block, offset, fragment->index,
 			fragment->offset, fragment->size, nlink);
-		for(i = 0; i < offset; i++) {
+		for(i = 0; i < offset; i++)
 			TRACE("Block %d, size %d\n", i, block_list[i]);
-			total_size += SQUASHFS_COMPRESSED_SIZE_BLOCK(block_list[i]);
-		}
 /* ANDROID CHANGES START*/
 #ifdef ANDROID
 		sub_path = subpathname(dir_ent);
@@ -1526,6 +1520,7 @@ again:
 	cache_block_put(compressed_buffer);
 
 finished:
+	do { } while (0);
 	pthread_cleanup_pop(0);
 
 	return buffer;
@@ -2142,7 +2137,7 @@ struct file_info *duplicate(long long file_size, long long bytes,
 }
 
 
-static inline int is_fragment(struct inode_info *inode)
+inline int is_fragment(struct inode_info *inode)
 {
 	off_t file_size = inode->buf.st_size;
 
@@ -2430,9 +2425,9 @@ void *writer(void *arg)
 		pthread_cleanup_push((void *) pthread_mutex_unlock, &pos_mutex);
 		pthread_mutex_lock(&pos_mutex);
 
-		if(lseek(fd, off, SEEK_SET) == -1) {
+		if(lseek(fd, off+squashfs_start_offset, SEEK_SET) == -1) {
 			ERROR("writer: Lseek on destination failed because "
-				"%s, offset=0x%llx\n", strerror(errno), off);
+				"%s, offset=0x%llx\n", strerror(errno), off+squashfs_start_offset);
 			BAD_ERROR("Probably out of space on output "
 				"%s\n", block_device ? "block device" :
 				"filesystem");
@@ -3121,19 +3116,19 @@ struct inode_info *lookup_inode3(struct stat *buf, int pseudo, int id,
 }
 
 
-static inline struct inode_info *lookup_inode2(struct stat *buf, int pseudo, int id)
+struct inode_info *lookup_inode2(struct stat *buf, int pseudo, int id)
 {
 	return lookup_inode3(buf, pseudo, id, NULL, 0);
 }
 
 
-static inline struct inode_info *lookup_inode(struct stat *buf)
+inline struct inode_info *lookup_inode(struct stat *buf)
 {
 	return lookup_inode2(buf, 0, 0);
 }
 
 
-static inline void alloc_inode_no(struct inode_info *inode, unsigned int use_this)
+inline void alloc_inode_no(struct inode_info *inode, unsigned int use_this)
 {
 	if (inode->inode_number == 0) {
 		inode->inode_number = use_this ? : inode_no ++;
@@ -3144,7 +3139,7 @@ static inline void alloc_inode_no(struct inode_info *inode, unsigned int use_thi
 }
 
 
-static inline struct dir_ent *create_dir_entry(char *name, char *source_name,
+inline struct dir_ent *create_dir_entry(char *name, char *source_name,
 	char *nonstandard_pathname, struct dir_info *dir)
 {
 	struct dir_ent *dir_ent = malloc(sizeof(struct dir_ent));
@@ -3167,8 +3162,15 @@ static inline struct dir_ent *create_dir_entry(char *name, char *source_name,
 }
 
 
+/* ANDROID CHANGES START*/
+#ifdef ANDROID
 static inline void add_dir_entry(struct dir_ent *dir_ent, struct dir_info *sub_dir,
 	struct inode_info *inode_info)
+#else
+inline void add_dir_entry(struct dir_ent *dir_ent, struct dir_info *sub_dir,
+	struct inode_info *inode_info)
+#endif
+/* ANDROID CHANGES END */
 {
 	struct dir_info *dir = dir_ent->our_dir;
 
@@ -3203,7 +3205,8 @@ static inline void add_dir_entry(struct dir_ent *dir_ent, struct dir_info *sub_d
 	dir->count++;
 }
 
-static inline void add_dir_entry2(char *name, char *source_name,
+
+inline void add_dir_entry2(char *name, char *source_name,
 	char *nonstandard_pathname, struct dir_info *sub_dir,
 	struct inode_info *inode_info, struct dir_info *dir)
 {
@@ -3215,7 +3218,7 @@ static inline void add_dir_entry2(char *name, char *source_name,
 }
 
 
-static inline void free_dir_entry(struct dir_ent *dir_ent)
+inline void free_dir_entry(struct dir_ent *dir_ent)
 {
 	if(dir_ent->name)
 		free(dir_ent->name);
@@ -3236,7 +3239,7 @@ static inline void free_dir_entry(struct dir_ent *dir_ent)
 }
 
 
-static inline void add_excluded(struct dir_info *dir)
+inline void add_excluded(struct dir_info *dir)
 {
 	dir->excluded ++;
 }
@@ -3757,6 +3760,12 @@ void dir_scan2(struct dir_info *dir, struct pseudo *pseudo)
 				pseudo_ent->pathname, NULL,
 				lookup_inode2(&buf, PSEUDO_FILE_PROCESS,
 				pseudo_ent->dev->pseudo_id), dir);
+		} else if(pseudo_ent->dev->type == 's') {
+			add_dir_entry2(pseudo_ent->name, NULL,
+				pseudo_ent->pathname, NULL,
+				lookup_inode3(&buf, PSEUDO_FILE_OTHER, 0,
+				pseudo_ent->dev->symlink,
+				strlen(pseudo_ent->dev->symlink) + 1), dir);
 		} else {
 			add_dir_entry2(pseudo_ent->name, NULL,
 				pseudo_ent->pathname, NULL,
@@ -4368,7 +4377,6 @@ void initialise_threads(int readq, int fragq, int bwriteq, int fwriteq,
 	sigemptyset(&sigmask);
 	sigaddset(&sigmask, SIGQUIT);
 	sigaddset(&sigmask, SIGHUP);
-	sigaddset(&sigmask, SIGALRM);
 	if(pthread_sigmask(SIG_BLOCK, &sigmask, NULL) == -1)
 		BAD_ERROR("Failed to set signal mask in intialise_threads\n");
 
@@ -4448,7 +4456,8 @@ void initialise_threads(int readq, int fragq, int bwriteq, int fwriteq,
 
 	main_thread = pthread_self();
 
-	printf("Parallel mksquashfs: Using %d processor%s\n", processors,
+	if(!quiet)
+		printf("Parallel mksquashfs: Using %d processor%s\n", processors,
 			processors == 1 ? "" : "s");
 
 	/* Restore the signal mask for the main thread */
@@ -5119,6 +5128,9 @@ void write_filesystem_tables(struct squashfs_super_block *sBlk, int nopad)
 	total_bytes += total_inode_bytes + total_directory_bytes +
 		sizeof(struct squashfs_super_block) + total_xattr_bytes;
 
+	if(quiet)
+		return;
+
 	printf("\n%sSquashfs %d.%d filesystem, %s compressed, data block size"
 		" %d\n", exportable ? "Exportable " : "", SQUASHFS_MAJOR,
 		SQUASHFS_MINOR, comp->name, block_size);
@@ -5184,9 +5196,6 @@ void write_filesystem_tables(struct squashfs_super_block *sBlk, int nopad)
 				group->gr_name, id_table[i]->id);
 		}
 	}
-	
-	printf("Number of whitelisted (uncompressed) files %d\n", 
-	       whitelisted_count);
 }
 
 
@@ -5299,47 +5308,20 @@ int parse_num(char *arg, int *res)
 
 int get_physical_memory()
 {
-	int phys_mem;
-#ifndef linux
-	#ifdef HW_MEMSIZE
-		#define SYSCTL_PHYSMEM HW_MEMSIZE
-	#elif defined(HW_PHYSMEM64)
-		#define SYSCTL_PHYSMEM HW_PHYSMEM64
-	#else
-		#define SYSCTL_PHYSMEM HW_PHYSMEM
-	#endif
-
-	int mib[2];
-	uint64_t sysctl_physmem = 0;
-	size_t sysctl_len = sizeof(sysctl_physmem);
-
-	mib[0] = CTL_HW;
-	mib[1] = SYSCTL_PHYSMEM;
-
-	if(sysctl(mib, 2, &sysctl_physmem, &sysctl_len, NULL, 0) == 0) {
-		/* some systems use 32-bit values, work with what we're given */
-		if (sysctl_len == 4)
-			sysctl_physmem = *(uint32_t*)&sysctl_physmem;
-		phys_mem = sysctl_physmem >> 20;
-	} else {
-		ERROR_START("Failed to get amount of available "
-			"memory.");
-		ERROR_EXIT("  Defaulting to least viable amount\n");
-		phys_mem = SQUASHFS_LOWMEM;
-	}
-  #undef SYSCTL_PHYSMEM
-#else
-	/* Long longs are used here because with PAE, a 32-bit
-	  machine can have more than 4GB of physical memory */
-
+	/*
+	 * Long longs are used here because with PAE, a 32-bit
+	 * machine can have more than 4GB of physical memory
+	 *
+	 * sysconf(_SC_PHYS_PAGES) relies on /proc being mounted.
+	 * If it isn't fail.
+	 */
 	long long num_pages = sysconf(_SC_PHYS_PAGES);
 	long long page_size = sysconf(_SC_PAGESIZE);
-	phys_mem = num_pages * page_size >> 20;
+	int phys_mem = num_pages * page_size >> 20;
+
 	if(num_pages == -1 || page_size == -1)
 		return 0;
 
-#endif
-
 	if(phys_mem < SQUASHFS_LOWMEM)
 		BAD_ERROR("Mksquashfs requires more physical memory than is "
 			"available!\n");
@@ -5442,8 +5424,8 @@ void calculate_queue_sizes(int mem, int *readq, int *fragq, int *bwriteq,
 
 
 #define VERSION() \
-	printf("mksquashfs version 4.3-git (2014/09/12)\n");\
-	printf("copyright (C) 2014 Phillip Lougher "\
+	printf("mksquashfs version 4.3-git (2017/07/18)\n");\
+	printf("copyright (C) 2017 Phillip Lougher "\
 		"<phillip@squashfs.org.uk>\n\n"); \
 	printf("This program is free software; you can redistribute it and/or"\
 		"\n");\
@@ -5698,6 +5680,15 @@ print_compressor_options:
 			force_progress = TRUE;
 		else if(strcmp(argv[i], "-no-exports") == 0)
 			exportable = FALSE;
+        else if(strcmp(argv[i], "-offset") == 0 ||
+				strcmp(argv[i], "-o") ==0) {
+			if(++i == argc) {
+				ERROR("%s: %s offset missing argument\n", argv[0],
+							argv[i - 1]);
+				exit(1);
+			}
+			squashfs_start_offset = (off_t)atol(argv[i]);
+        }        
 		else if(strcmp(argv[i], "-processors") == 0) {
 			if((++i == argc) || !parse_num(argv[i], &processors)) {
 				ERROR("%s: -processors missing or invalid "
@@ -5931,8 +5922,12 @@ print_compressor_options:
 		else if(strcmp(argv[i], "-noappend") == 0)
 			delete = TRUE;
 
+		else if(strcmp(argv[i], "-quiet") == 0)
+			quiet = TRUE;
+
 		else if(strcmp(argv[i], "-keep-as-directory") == 0)
 			keep_as_directory = TRUE;
+
 /* ANDROID CHANGES START*/
 #ifdef ANDROID
 		else if(strcmp(argv[i], "-android-fs-config") == 0)
@@ -5975,7 +5970,6 @@ print_compressor_options:
 		}
 #endif
 /* ANDROID CHANGES END */
-
 		else if(strcmp(argv[i], "-exit-on-error") == 0)
 			exit_on_error = TRUE;
 
@@ -6062,6 +6056,14 @@ printOptions:
 				"definition\n");
 			ERROR("-pf <pseudo-file>\tAdd list of pseudo file "
 				"definitions\n");
+			ERROR("\t\t\tPseudo definitions should be of the "
+				"format\n");
+			ERROR("\t\t\t\tfilename d mode uid gid\n");
+			ERROR("\t\t\t\tfilename m mode uid gid\n");
+			ERROR("\t\t\t\tfilename b mode uid gid major minor\n");
+			ERROR("\t\t\t\tfilename c mode uid gid major minor\n");
+			ERROR("\t\t\t\tfilename f mode uid gid command\n");
+			ERROR("\t\t\t\tfilename s mode uid gid symlink\n");
 			ERROR("-sort <sort_file>\tsort files according to "
 				"priorities in <sort_file>.  One\n");
 			ERROR("\t\t\tfile or dir with priority per line.  "
@@ -6093,6 +6095,7 @@ printOptions:
 				"using recovery file <name>\n");
 			ERROR("-no-recovery\t\tdon't generate a recovery "
 				"file\n");
+			ERROR("-quiet\t\t\tno verbose output\n");
 			ERROR("-info\t\t\tprint files written to filesystem\n");
 			ERROR("-no-progress\t\tdon't display the progress "
 				"bar\n");
@@ -6109,6 +6112,9 @@ printOptions:
 			ERROR("\nMiscellaneous options:\n");
 			ERROR("-root-owned\t\talternative name for -all-root"
 				"\n");
+			ERROR("-o <offset>\t\tSkip <offset> bytes at the "
+				"beginning of the file.\n\t\t\t"
+				"Default 0 bytes\n");            
 			ERROR("-noInodeCompression\talternative name for -noI"
 				"\n");
 			ERROR("-noDataCompression\talternative name for -noD"
@@ -6301,8 +6307,10 @@ printOptions:
 		void *comp_data = compressor_dump_options(comp, block_size,
 			&size);
 
-		printf("Creating %d.%d filesystem on %s, block size %d.\n",
-			SQUASHFS_MAJOR, SQUASHFS_MINOR, argv[source + 1], block_size);
+		if(!quiet)
+			printf("Creating %d.%d filesystem on %s, block size %d.\n",
+				SQUASHFS_MAJOR, SQUASHFS_MINOR,
+				argv[source + 1], block_size);
 
 		/*
 		 * store any compressor specific options after the superblock,
diff --git a/squashfs-tools/mksquashfs.h b/squashfs-tools/mksquashfs.h
index bfbf0bf..0a091cb 100644
--- a/squashfs-tools/mksquashfs.h
+++ b/squashfs-tools/mksquashfs.h
@@ -29,7 +29,6 @@
 #include <stdint.h>
 #endif
 /* ANDROID CHANGES END */
-#include <pthread.h>
 
 struct dir_info {
 	char			*pathname;
diff --git a/squashfs-tools/process_fragments.c b/squashfs-tools/process_fragments.c
index bba6f5a..971dc11 100644
--- a/squashfs-tools/process_fragments.c
+++ b/squashfs-tools/process_fragments.c
@@ -210,6 +210,7 @@ again:
 	cache_block_put(compressed_buffer);
 
 finished:
+	do { } while (0);
 	pthread_cleanup_pop(0);
 
 	return buffer;
diff --git a/squashfs-tools/pseudo.c b/squashfs-tools/pseudo.c
index e12d399..cb74cf6 100644
--- a/squashfs-tools/pseudo.c
+++ b/squashfs-tools/pseudo.c
@@ -2,7 +2,7 @@
  * Create a squashfs filesystem.  This is a highly compressed read only
  * filesystem.
  *
- * Copyright (c) 2009, 2010, 2012, 2014
+ * Copyright (c) 2009, 2010, 2012, 2014, 2017
  * Phillip Lougher <phillip@squashfs.org.uk>
  *
  * This program is free software; you can redistribute it and/or
@@ -30,9 +30,9 @@
 #include <errno.h>
 #include <string.h>
 #include <stdlib.h>
-#include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <sys/stat.h>
 #include <ctype.h>
 
 #include "pseudo.h"
@@ -274,6 +274,7 @@ struct pseudo_dev *get_pseudo_file(int pseudo_id)
 int read_pseudo_def(char *def)
 {
 	int n, bytes;
+	int quoted = 0;
 	unsigned int major = 0, minor = 0, mode;
 	char type, *ptr;
 	char suid[100], sgid[100]; /* overflow safe */
@@ -284,13 +285,22 @@ int read_pseudo_def(char *def)
 
 	/*
 	 * Scan for filename, don't use sscanf() and "%s" because
-	 * that can't handle filenames with spaces
+	 * that can't handle filenames with spaces.
+	 *
+	 * Filenames with spaces should either escape (backslash) the
+	 * space or use double quotes.
 	 */
 	filename = malloc(strlen(def) + 1);
 	if(filename == NULL)
 		MEM_ERROR();
 
-	for(name = filename; !isspace(*def) && *def != '\0';) {
+	for(name = filename; (quoted || !isspace(*def)) && *def != '\0';) {
+		if(*def == '"') {
+			quoted = !quoted;
+			def ++;
+			continue;
+		}
+
 		if(*def == '\\') {
 			def ++;
 			if (*def == '\0')
@@ -317,12 +327,11 @@ int read_pseudo_def(char *def)
 		case -1:
 			/* FALLTHROUGH */
 		case 0:
-			ERROR("Read filename, but failed to read or match "
-				"type\n");
-			break;
+			/* FALLTHROUGH */
 		case 1:
-			ERROR("Read filename and type, but failed to read or "
-				"match octal mode\n");
+			ERROR("Couldn't parse filename, type or octal mode\n");
+			ERROR("If the filename has spaces, either quote it, or "
+				"backslash the spaces\n");
 			break;
 		case 2:
 			ERROR("Read filename, type and mode, but failed to "
@@ -388,6 +397,20 @@ int read_pseudo_def(char *def)
 			goto error;
 		}	
 		break;
+	case 's':
+		if(def[0] == '\0') {
+			ERROR("Not enough arguments in symlink pseudo "
+				"definition \"%s\"\n", orig_def);
+			ERROR("Expected symlink\n");
+			goto error;
+		}
+
+		if(strlen(def) > 65535) {
+			ERROR("Symlink pseudo definition %s is greater than 65535"
+								" bytes!\n", def);
+			goto error;
+		}
+		break;
 	default:
 		ERROR("Unsupported type %c\n", type);
 		goto error;
@@ -444,6 +467,10 @@ int read_pseudo_def(char *def)
 	case 'f':
 		mode |= S_IFREG;
 		break;
+	case 's':
+		/* permissions on symlinks are always rwxrwxrwx */
+		mode = 0777 | S_IFLNK;
+		break;
 	}
 
 	dev = malloc(sizeof(struct pseudo_dev));
@@ -460,6 +487,8 @@ int read_pseudo_def(char *def)
 		dev->command = strdup(def);
 		add_pseudo_file(dev);
 	}
+	if(type == 's')
+		dev->symlink = strdup(def);
 
 	pseudo = add_pseudo(pseudo, dev, filename, filename);
 
@@ -467,12 +496,13 @@ int read_pseudo_def(char *def)
 	return TRUE;
 
 error:
-	ERROR("Pseudo definitions should be of format\n");
+	ERROR("Pseudo definitions should be of the format\n");
 	ERROR("\tfilename d mode uid gid\n");
 	ERROR("\tfilename m mode uid gid\n");
 	ERROR("\tfilename b mode uid gid major minor\n");
 	ERROR("\tfilename c mode uid gid major minor\n");
-	ERROR("\tfilename f mode uid command\n");
+	ERROR("\tfilename f mode uid gid command\n");
+	ERROR("\tfilename s mode uid gid symlink\n");
 	free(filename);
 	return FALSE;
 }
diff --git a/squashfs-tools/pseudo.h b/squashfs-tools/pseudo.h
index c0d9f6f..ef693c3 100644
--- a/squashfs-tools/pseudo.h
+++ b/squashfs-tools/pseudo.h
@@ -31,7 +31,10 @@ struct pseudo_dev {
 	unsigned int	major;
 	unsigned int	minor;
 	int		pseudo_id;
-	char		*command;
+	union {
+		char		*command;
+		char		*symlink;
+	};
 };
 
 struct pseudo_entry {
diff --git a/squashfs-tools/read_xattrs.c b/squashfs-tools/read_xattrs.c
index 837d3fb..42106f5 100644
--- a/squashfs-tools/read_xattrs.c
+++ b/squashfs-tools/read_xattrs.c
@@ -39,13 +39,13 @@
 #include <endian.h>
 #endif
 
-#include <stdlib.h>
-
 #include "squashfs_fs.h"
 #include "squashfs_swap.h"
 #include "xattr.h"
 #include "error.h"
 
+#include <stdlib.h>
+
 extern int read_fs_bytes(int, long long, int, void *);
 extern int read_block(int, long long, long long *, int, void *);
 
diff --git a/squashfs-tools/squashfs_fs.h b/squashfs-tools/squashfs_fs.h
index 791fe12..afca918 100644
--- a/squashfs-tools/squashfs_fs.h
+++ b/squashfs-tools/squashfs_fs.h
@@ -277,6 +277,7 @@ typedef long long		squashfs_inode;
 #define LZO_COMPRESSION		3
 #define XZ_COMPRESSION		4
 #define LZ4_COMPRESSION		5
+#define ZSTD_COMPRESSION	6
 
 struct squashfs_super_block {
 	unsigned int		s_magic;
diff --git a/squashfs-tools/unsquashfs.c b/squashfs-tools/unsquashfs.c
index 0dbc4c2..c5e0876 100644
--- a/squashfs-tools/unsquashfs.c
+++ b/squashfs-tools/unsquashfs.c
@@ -30,13 +30,9 @@
 #include "xattr.h"
 #include "unsquashfs_info.h"
 #include "stdarg.h"
+#include "fnmatch_compat.h"
 
-#ifndef linux
-#include <sys/sysctl.h>
-#else
 #include <sys/sysinfo.h>
-#endif
-
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
@@ -47,6 +43,7 @@ struct cache *fragment_cache, *data_cache;
 struct queue *to_reader, *to_inflate, *to_writer, *from_writer;
 pthread_t *thread, *inflator_thread;
 pthread_mutex_t	fragment_mutex;
+static off_t squashfs_start_offset = 0;
 
 /* user options that control parallelisation */
 int processors = -1;
@@ -636,7 +633,7 @@ int read_fs_bytes(int fd, long long byte, int bytes, void *buff)
 	TRACE("read_bytes: reading from position 0x%llx, bytes %d\n", byte,
 		bytes);
 
-	if(lseek(fd, off, SEEK_SET) == -1) {
+	if(lseek(fd, off + squashfs_start_offset, SEEK_SET) == -1) {
 		ERROR("Lseek failed because %s\n", strerror(errno));
 		return FALSE;
 	}
@@ -1122,7 +1119,11 @@ int create_inode(char *pathname, struct inode *i)
 	 	case SQUASHFS_CHRDEV_TYPE:
  		case SQUASHFS_LBLKDEV_TYPE:
 	 	case SQUASHFS_LCHRDEV_TYPE: {
-			int chrdev = i->type == SQUASHFS_CHRDEV_TYPE;
+			int chrdev = 0;
+			if ( i->type == SQUASHFS_CHRDEV_TYPE ||
+					i->type == SQUASHFS_LCHRDEV_TYPE)
+				chrdev = 1;
+
 			TRACE("create_inode: dev, rdev 0x%llx\n", i->data);
 
 			if(root_process) {
@@ -1645,9 +1646,9 @@ void squashfs_stat(char *source)
 
 	printf("Creation or last append time %s", mkfs_str ? mkfs_str :
 		"failed to get time\n");
-	printf("Filesystem size %.2f Kbytes (%.2f Mbytes)\n",
-		sBlk.s.bytes_used / 1024.0, sBlk.s.bytes_used /
-		(1024.0 * 1024.0));
+	printf("Filesystem size %llu bytes (%.2f Kbytes / %.2f Mbytes)\n",
+		sBlk.s.bytes_used, sBlk.s.bytes_used / 1024.0,
+		sBlk.s.bytes_used / (1024.0 * 1024.0));
 
 	if(sBlk.s.s_major == 4) {
 		printf("Compression %s\n", comp->name);
@@ -2179,7 +2180,6 @@ void initialise_threads(int fragment_buffer_size, int data_buffer_size)
 	sigemptyset(&sigmask);
 	sigaddset(&sigmask, SIGQUIT);
 	sigaddset(&sigmask, SIGHUP);
-	sigaddset(&sigmask, SIGALRM);
 	if(pthread_sigmask(SIG_BLOCK, &sigmask, NULL) == -1)
 		EXIT_UNSQUASH("Failed to set signal mask in initialise_threads"
 			"\n");
@@ -2550,6 +2550,14 @@ int main(int argc, char *argv[])
 				exit(1);
 			}
 			dest = argv[i];
+        		} else if (strcmp(argv[i], "-offset") == 0 ||
+				strcmp(argv[i], "-o") == 0) {
+			if(++i == argc) {
+				fprintf(stderr, "%s: -offset missing argument\n",
+					argv[0]);
+				exit(1);
+			}
+			squashfs_start_offset = (off_t)atol(argv[i]);
 		} else if(strcmp(argv[i], "-processors") == 0 ||
 				strcmp(argv[i], "-p") == 0) {
 			if((++i == argc) || 
@@ -2642,6 +2650,8 @@ options:
 				"copyright information\n");
 			ERROR("\t-d[est] <pathname>\tunsquash to <pathname>, "
 				"default \"squashfs-root\"\n");
+			ERROR("\t-o[ffset] <bytes>\tskip <bytes> at start of input file, "
+				"default \"0\"\n");
 			ERROR("\t-n[o-progress]\t\tdon't display the progress "
 				"bar\n");
 			ERROR("\t-no[-xattrs]\t\tdon't extract xattrs in file system"
diff --git a/squashfs-tools/unsquashfs.h b/squashfs-tools/unsquashfs.h
index 4836b8d..0edbd25 100644
--- a/squashfs-tools/unsquashfs.h
+++ b/squashfs-tools/unsquashfs.h
@@ -40,17 +40,12 @@
 #include <grp.h>
 #include <time.h>
 #include <regex.h>
-#include <fnmatch.h>
 #include <signal.h>
 #include <pthread.h>
 #include <math.h>
 #include <sys/ioctl.h>
 #include <sys/time.h>
 
-#ifndef FNM_EXTMATCH /* glibc extension */
-    #define FNM_EXTMATCH 0
-#endif
-
 #ifndef linux
 #define __BYTE_ORDER BYTE_ORDER
 #define __BIG_ENDIAN BIG_ENDIAN
diff --git a/squashfs-tools/unsquashfs_info.c b/squashfs-tools/unsquashfs_info.c
index 7d4f7af..c8e2b9b 100644
--- a/squashfs-tools/unsquashfs_info.c
+++ b/squashfs-tools/unsquashfs_info.c
@@ -97,22 +97,31 @@ void dump_state()
 void *info_thrd(void *arg)
 {
 	sigset_t sigmask;
-	int sig, err, waiting = 0;
+	struct timespec timespec = { .tv_sec = 1, .tv_nsec = 0 };
+	int sig, waiting = 0;
 
 	sigemptyset(&sigmask);
 	sigaddset(&sigmask, SIGQUIT);
 	sigaddset(&sigmask, SIGHUP);
-	sigaddset(&sigmask, SIGALRM);
 
 	while(1) {
-		err = sigwait(&sigmask, &sig);
+		if(waiting)
+			sig = sigtimedwait(&sigmask, NULL, &timespec);
+		else
+			sig = sigwaitinfo(&sigmask, NULL);
 
-		if(err == -1) {
+		if(sig == -1) {
 			switch(errno) {
+			case EAGAIN:
+				/* interval timed out */
+				waiting = 0;
+				/* FALLTHROUGH */
 			case EINTR:
+				/* if waiting, the wait will be longer, but
+				   that's OK */
 				continue;
 			default:
-				BAD_ERROR("sigwait failed "
+				BAD_ERROR("sigtimedwait/sigwaitinfo failed "
 					"because %s\n", strerror(errno));
 			}
 		}
@@ -124,12 +133,8 @@ void *info_thrd(void *arg)
 			/* set one second interval period, if ^\ received
 			   within then, dump queue and cache status */
 			waiting = 1;
-			alarm(1);
-		} else if (sig == SIGQUIT) {
+		} else
 			dump_state();
-		} else if (sig == SIGALRM) {
-			waiting = 0;
-		}
 	}
 }
 
diff --git a/squashfs-tools/unsquashfs_xattr.c b/squashfs-tools/unsquashfs_xattr.c
index 13f0e35..59f4aae 100644
--- a/squashfs-tools/unsquashfs_xattr.c
+++ b/squashfs-tools/unsquashfs_xattr.c
@@ -27,11 +27,6 @@
 
 #include <sys/xattr.h>
 
-#ifdef XATTR_NOFOLLOW /* Apple's xattrs */
-    #define lsetxattr(path_, name_, val_, sz_, flags_) \
-        setxattr(path_, name_, val_, sz_, 0, flags_ | XATTR_NOFOLLOW)
-#endif
-
 #define NOSPACE_MAX 10
 
 extern int root_process;
diff --git a/squashfs-tools/xattr.c b/squashfs-tools/xattr.c
index 6cecb74..c34b2a7 100644
--- a/squashfs-tools/xattr.c
+++ b/squashfs-tools/xattr.c
@@ -22,14 +22,6 @@
  * xattr.c
  */
 
-#ifndef linux
-#define __BYTE_ORDER BYTE_ORDER
-#define __BIG_ENDIAN BIG_ENDIAN
-#define __LITTLE_ENDIAN LITTLE_ENDIAN
-#else
-#include <endian.h>
-#endif
-
 #define TRUE 1
 #define FALSE 0
 
@@ -44,13 +36,6 @@
 #include <stdlib.h>
 #include <sys/xattr.h>
 
-#ifdef XATTR_NOFOLLOW /* Apple's xattrs */
-    #define llistxattr(path_, buf_, sz_) \
-        listxattr(path_, buf_, sz_, XATTR_NOFOLLOW)
-    #define lgetxattr(path_, name_, val_, sz_) \
-        getxattr(path_, name_, val_, sz_, 0, XATTR_NOFOLLOW)
-#endif
-
 #include "squashfs_fs.h"
 #include "squashfs_swap.h"
 #include "mksquashfs.h"
diff --git a/squashfs-tools/xz_wrapper.c b/squashfs-tools/xz_wrapper.c
index e77ec59..0977f74 100644
--- a/squashfs-tools/xz_wrapper.c
+++ b/squashfs-tools/xz_wrapper.c
@@ -322,7 +322,7 @@ failed:
 }
 
 
-void xz_display_options(void *buffer, int size)
+static void xz_display_options(void *buffer, int size)
 {
 	struct comp_opts *comp_opts = buffer;
 	int dictionary_size, flags, printed;
@@ -503,7 +503,7 @@ static int xz_uncompress(void *dest, void *src, int size, int outsize,
 }
 
 
-void xz_usage()
+static void xz_usage()
 {
 	fprintf(stderr, "\t  -Xbcj filter1,filter2,...,filterN\n");
 	fprintf(stderr, "\t\tCompress using filter1,filter2,...,filterN in");
diff --git a/squashfs-tools/zstd_wrapper.c b/squashfs-tools/zstd_wrapper.c
new file mode 100644
index 0000000..dcab75a
--- /dev/null
+++ b/squashfs-tools/zstd_wrapper.c
@@ -0,0 +1,254 @@
+/*
+ * Copyright (c) 2017
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * zstd_wrapper.c
+ *
+ * Support for ZSTD compression http://zstd.net
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <zstd.h>
+#include <zstd_errors.h>
+
+#include "squashfs_fs.h"
+#include "zstd_wrapper.h"
+#include "compressor.h"
+
+static int compression_level = ZSTD_DEFAULT_COMPRESSION_LEVEL;
+
+/*
+ * This function is called by the options parsing code in mksquashfs.c
+ * to parse any -X compressor option.
+ *
+ * This function returns:
+ *	>=0 (number of additional args parsed) on success
+ *	-1 if the option was unrecognised, or
+ *	-2 if the option was recognised, but otherwise bad in
+ *	   some way (e.g. invalid parameter)
+ *
+ * Note: this function sets internal compressor state, but does not
+ * pass back the results of the parsing other than success/failure.
+ * The zstd_dump_options() function is called later to get the options in
+ * a format suitable for writing to the filesystem.
+ */
+static int zstd_options(char *argv[], int argc)
+{
+	if (strcmp(argv[0], "-Xcompression-level") == 0) {
+		if (argc < 2) {
+			fprintf(stderr, "zstd: -Xcompression-level missing "
+				"compression level\n");
+			fprintf(stderr, "zstd: -Xcompression-level it should "
+				"be 1 <= n <= %d\n", ZSTD_maxCLevel());
+			goto failed;
+		}
+
+		compression_level = atoi(argv[1]);
+		if (compression_level < 1 ||
+		    compression_level > ZSTD_maxCLevel()) {
+			fprintf(stderr, "zstd: -Xcompression-level invalid, it "
+				"should be 1 <= n <= %d\n", ZSTD_maxCLevel());
+			goto failed;
+		}
+
+		return 1;
+	}
+
+	return -1;
+failed:
+	return -2;
+}
+
+/*
+ * This function is called by mksquashfs to dump the parsed
+ * compressor options in a format suitable for writing to the
+ * compressor options field in the filesystem (stored immediately
+ * after the superblock).
+ *
+ * This function returns a pointer to the compression options structure
+ * to be stored (and the size), or NULL if there are no compression
+ * options.
+ */
+static void *zstd_dump_options(int block_size, int *size)
+{
+	static struct zstd_comp_opts comp_opts;
+
+	/* don't return anything if the options are all default */
+	if (compression_level == ZSTD_DEFAULT_COMPRESSION_LEVEL)
+		return NULL;
+
+	comp_opts.compression_level = compression_level;
+
+	SQUASHFS_INSWAP_COMP_OPTS(&comp_opts);
+
+	*size = sizeof(comp_opts);
+	return &comp_opts;
+}
+
+/*
+ * This function is a helper specifically for the append mode of
+ * mksquashfs.  Its purpose is to set the internal compressor state
+ * to the stored compressor options in the passed compressor options
+ * structure.
+ *
+ * In effect this function sets up the compressor options
+ * to the same state they were when the filesystem was originally
+ * generated, this is to ensure on appending, the compressor uses
+ * the same compression options that were used to generate the
+ * original filesystem.
+ *
+ * Note, even if there are no compressor options, this function is still
+ * called with an empty compressor structure (size == 0), to explicitly
+ * set the default options, this is to ensure any user supplied
+ * -X options on the appending mksquashfs command line are over-ridden.
+ *
+ * This function returns 0 on sucessful extraction of options, and -1 on error.
+ */
+static int zstd_extract_options(int block_size, void *buffer, int size)
+{
+	struct zstd_comp_opts *comp_opts = buffer;
+
+	if (size == 0) {
+		/* Set default values */
+		compression_level = ZSTD_DEFAULT_COMPRESSION_LEVEL;
+		return 0;
+	}
+
+	/* we expect a comp_opts structure of sufficient size to be present */
+	if (size < sizeof(*comp_opts))
+		goto failed;
+
+	SQUASHFS_INSWAP_COMP_OPTS(comp_opts);
+
+	if (comp_opts->compression_level < 1 ||
+	    comp_opts->compression_level > ZSTD_maxCLevel()) {
+		fprintf(stderr, "zstd: bad compression level in compression "
+			"options structure\n");
+		goto failed;
+	}
+
+	compression_level = comp_opts->compression_level;
+
+	return 0;
+
+failed:
+	fprintf(stderr, "zstd: error reading stored compressor options from "
+		"filesystem!\n");
+
+	return -1;
+}
+
+static void zstd_display_options(void *buffer, int size)
+{
+	struct zstd_comp_opts *comp_opts = buffer;
+
+	/* we expect a comp_opts structure of sufficient size to be present */
+	if (size < sizeof(*comp_opts))
+		goto failed;
+
+	SQUASHFS_INSWAP_COMP_OPTS(comp_opts);
+
+	if (comp_opts->compression_level < 1 ||
+	    comp_opts->compression_level > ZSTD_maxCLevel()) {
+		fprintf(stderr, "zstd: bad compression level in compression "
+			"options structure\n");
+		goto failed;
+	}
+
+	printf("\tcompression-level %d\n", comp_opts->compression_level);
+
+	return;
+
+failed:
+	fprintf(stderr, "zstd: error reading stored compressor options from "
+		"filesystem!\n");
+}
+
+/*
+ * This function is called by mksquashfs to initialise the
+ * compressor, before compress() is called.
+ *
+ * This function returns 0 on success, and -1 on error.
+ */
+static int zstd_init(void **strm, int block_size, int datablock)
+{
+	ZSTD_CCtx *cctx = ZSTD_createCCtx();
+
+	if (!cctx) {
+		fprintf(stderr, "zstd: failed to allocate compression "
+			"context!\n");
+		return -1;
+	}
+
+	*strm = cctx;
+	return 0;
+}
+
+static int zstd_compress(void *strm, void *dest, void *src, int size,
+			 int block_size, int *error)
+{
+	const size_t res = ZSTD_compressCCtx((ZSTD_CCtx*)strm, dest, block_size,
+					     src, size, compression_level);
+
+	if (ZSTD_isError(res)) {
+		/* FIXME:
+		 * zstd does not expose stable error codes. The error enum may
+		 * change between versions. Until upstream zstd stablizes the
+		 * error codes, we have no way of knowing why the error occurs.
+		 * zstd shouldn't fail to compress any input unless there isn't
+		 * enough output space. We assume that is the cause and return
+		 * the special error code for not enough output space.
+		 */
+		return 0;
+	}
+
+	return (int)res;
+}
+
+static int zstd_uncompress(void *dest, void *src, int size, int outsize,
+			   int *error)
+{
+	const size_t res = ZSTD_decompress(dest, outsize, src, size);
+
+	if (ZSTD_isError(res)) {
+		fprintf(stderr, "\t%d %d\n", outsize, size);
+
+		*error = (int)ZSTD_getErrorCode(res);
+		return -1;
+	}
+
+	return (int)res;
+}
+
+static void zstd_usage(void)
+{
+	fprintf(stderr, "\t  -Xcompression-level <compression-level>\n");
+	fprintf(stderr, "\t\t<compression-level> should be 1 .. %d (default "
+		"%d)\n", ZSTD_maxCLevel(), ZSTD_DEFAULT_COMPRESSION_LEVEL);
+}
+
+struct compressor zstd_comp_ops = {
+	.init = zstd_init,
+	.compress = zstd_compress,
+	.uncompress = zstd_uncompress,
+	.options = zstd_options,
+	.dump_options = zstd_dump_options,
+	.extract_options = zstd_extract_options,
+	.display_options = zstd_display_options,
+	.usage = zstd_usage,
+	.id = ZSTD_COMPRESSION,
+	.name = "zstd",
+	.supported = 1
+};
diff --git a/squashfs-tools/zstd_wrapper.h b/squashfs-tools/zstd_wrapper.h
new file mode 100644
index 0000000..4fbef0a
--- /dev/null
+++ b/squashfs-tools/zstd_wrapper.h
@@ -0,0 +1,48 @@
+#ifndef ZSTD_WRAPPER_H
+#define ZSTD_WRAPPER_H
+/*
+ * Squashfs
+ *
+ * Copyright (c) 2017
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * zstd_wrapper.h
+ *
+ */
+
+#ifndef linux
+#define __BYTE_ORDER BYTE_ORDER
+#define __BIG_ENDIAN BIG_ENDIAN
+#define __LITTLE_ENDIAN LITTLE_ENDIAN
+#else
+#include <endian.h>
+#endif
+
+#if __BYTE_ORDER == __BIG_ENDIAN
+extern unsigned int inswap_le16(unsigned short);
+extern unsigned int inswap_le32(unsigned int);
+
+#define SQUASHFS_INSWAP_COMP_OPTS(s) { \
+	(s)->compression_level = inswap_le32((s)->compression_level); \
+}
+#else
+#define SQUASHFS_INSWAP_COMP_OPTS(s)
+#endif
+
+/* Default compression */
+#define ZSTD_DEFAULT_COMPRESSION_LEVEL 15
+
+struct zstd_comp_opts {
+	int compression_level;
+};
+#endif