Docs: Add new example programs.

These have more comments than the old examples and
human-readable error messages. More tutorial-like examples
are needed but these are a start.

5 files changed, 827 insertions, 0 deletions

diff --git a/doc/examples/00_README.txt b/doc/examples/00_README.txt
new file mode 100644
index 00000000..a3b9eaa1
--- /dev/null
+++ b/doc/examples/00_README.txt
@@ -0,0 +1,27 @@
+
+liblzma example programs
+========================
+
+Introduction
+
+    The examples are written so that the same comments aren't
+    repeated (much) in later files.
+
+    On POSIX systems, the examples should build by just typing "make".
+
+    The examples that use stdin or stdout don't set stdin and stdout
+    to binary mode. On systems where it matters (e.g. Windows) it is
+    possible that the examples won't work without modification.
+
+
+List of examples
+
+    01_compress_easy.c                  Multi-call compression using
+                                        a compression preset
+
+    02_decompress.c                     Multi-call decompression
+
+    03_compress_custom.c                Like 01_compress_easy.c but using
+                                        a custom filter chain
+                                        (x86 BCJ + LZMA2)
+
diff --git a/doc/examples/01_compress_easy.c b/doc/examples/01_compress_easy.c
new file mode 100644
index 00000000..f79cade1
--- /dev/null
+++ b/doc/examples/01_compress_easy.c
@@ -0,0 +1,297 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       01_compress_easy.c
+/// \brief      Compress from stdin to stdout in multi-call mode
+///
+/// Usage:      ./01_compress_easy PRESET < INFILE > OUTFILE
+///
+/// Example:    ./01_compress_easy 6 < foo > foo.xz
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <lzma.h>
+
+
+static void
+show_usage_and_exit(const char *argv0)
+{
+	fprintf(stderr, "Usage: %s PRESET < INFILE > OUTFILE\n"
+			"PRESET is a number 0-9 and can optionally be "
+			"by `e' to indicate extreme preset\n",
+			argv0);
+	exit(EXIT_FAILURE);
+}
+
+
+static uint32_t
+get_preset(int argc, char **argv)
+{
+	// One argument whose first char must be 0-9.
+	if (argc != 2 || argv[1][0] < '0' || argv[1][0] > '9')
+		show_usage_and_exit(argv[0]);
+
+	// Calculate the preste level 0-9.
+	uint32_t preset = argv[1][0] - '0';
+
+	// If there is a second char, it must be 'e'. It will set
+	// the LZMA_PRESET_EXTREME flag.
+	if (argv[1][1] != '\0') {
+		if (argv[1][1] != 'e' || argv[1][2] != '\0')
+			show_usage_and_exit(argv[0]);
+
+		preset |= LZMA_PRESET_EXTREME;
+	}
+
+	return preset;
+}
+
+
+static bool
+init_encoder(lzma_stream *strm, uint32_t preset)
+{
+	// Initialize the encoder using a preset. Set the integrity to check
+	// to CRC64, which is the default in the xz command line tool. If
+	// the .xz file needs to be decompressed with XZ Embedded, use
+	// LZMA_CHECK_CRC32 instead.
+	lzma_ret ret = lzma_easy_encoder(strm, preset, LZMA_CHECK_CRC64);
+
+	// Return successfully if the initialization went fine.
+	if (ret == LZMA_OK)
+		return true;
+
+	// Something went wrong. The possible errors are documented in
+	// lzma/container.h (src/liblzma/api/lzma/container.h in the source
+	// package or e.g. /usr/include/lzma/container.h depending on the
+	// install prefix).
+	const char *msg;
+	switch (ret) {
+	case LZMA_MEM_ERROR:
+		msg = "Memory allocation failed";
+		break;
+
+	case LZMA_OPTIONS_ERROR:
+		msg = "Specified preset is not supported";
+		break;
+
+	case LZMA_UNSUPPORTED_CHECK:
+		msg = "Specified integrity check is not supported";
+		break;
+
+	default:
+		// This is most likely LZMA_PROG_ERROR indicating a bug in
+		// this program or in liblzma. It is inconvenient to have a
+		// separate error message for errors that should be impossible
+		// to occur, but knowing the error code is important for
+		// debugging. That's why it is good to print the error code
+		// at least when there is no good error message to show.
+		msg = "Unknown error, possibly a bug";
+		break;
+	}
+
+	fprintf(stderr, "Error initializing the encoder: %s (error code %u)\n",
+			msg, ret);
+	return false;
+}
+
+
+static bool
+compress(lzma_stream *strm, FILE *infile, FILE *outfile)
+{
+	// This will be LZMA_RUN until the end of the input file is reached.
+	// This tells lzma_code() when there will be no more input.
+	lzma_action action = LZMA_RUN;
+
+	// Buffers to temporarily hold uncompressed input
+	// and compressed output.
+	uint8_t inbuf[BUFSIZ];
+	uint8_t outbuf[BUFSIZ];
+
+	// Initialize the input and output pointers. Initializing next_in
+	// and avail_in isn't really necessary when we are going to encode
+	// just one file since LZMA_STREAM_INIT takes care of initializing
+	// those already. But it doesn't hurt much and it will be needed
+	// if encoding more than one file like we will in 02_decompress.c.
+	//
+	// While we don't care about strm->total_in or strm->total_out in this
+	// example, it is worth noting that initializing the encoder will
+	// always reset total_in and total_out to zero. But the encoder
+	// initialization doesn't touch next_in, avail_in, next_out, or
+	// avail_out.
+	strm->next_in = NULL;
+	strm->avail_in = 0;
+	strm->next_out = outbuf;
+	strm->avail_out = sizeof(outbuf);
+
+	// Loop until the file has been successfully compressed or until
+	// an error occurs.
+	while (true) {
+		// Fill the input buffer if it is empty.
+		if (strm->avail_in == 0 && !feof(infile)) {
+			strm->next_in = inbuf;
+			strm->avail_in = fread(inbuf, 1, sizeof(inbuf),
+					infile);
+
+			if (ferror(infile)) {
+				fprintf(stderr, "Read error: %s\n",
+						strerror(errno));
+				return false;
+			}
+
+			// Once the end of the input file has been reached,
+			// we need to tell lzma_code() that no more input
+			// will be coming and that it should finish the
+			// encoding.
+			if (feof(infile))
+				action = LZMA_FINISH;
+		}
+
+		// Tell liblzma do the actual encoding.
+		//
+		// This reads up to strm->avail_in bytes of input starting
+		// from strm->next_in. avail_in will be decremented and
+		// next_in incremented by an equal amount to match the
+		// number of input bytes consumed.
+		//
+		// Up to strm->avail_out bytes of compressed output will be
+		// written starting from strm->next_out. avail_out and next_out
+		// will be incremented by an equal amount to match the number
+		// of output bytes written.
+		//
+		// The encoder has to do internal buffering, which means that
+		// it may take quite a bit of input before the same data is
+		// available in compressed form in the output buffer.
+		lzma_ret ret = lzma_code(strm, action);
+
+		// If the output buffer is full or if the compression finished
+		// successfully, write the data from the output bufffer to
+		// the output file.
+		if (strm->avail_out == 0 || ret == LZMA_STREAM_END) {
+			// When lzma_code() has returned LZMA_STREAM_END,
+			// the output buffer is likely to be only partially
+			// full. Calculate how much new data there is to
+			// be written to the output file.
+			size_t write_size = sizeof(outbuf) - strm->avail_out;
+
+			if (fwrite(outbuf, 1, write_size, outfile)
+					!= write_size) {
+				fprintf(stderr, "Write error: %s\n",
+						strerror(errno));
+				return false;
+			}
+
+			// Reset next_out and avail_out.
+			strm->next_out = outbuf;
+			strm->avail_out = sizeof(outbuf);
+		}
+
+		// Normally the return value of lzma_code() will be LZMA_OK
+		// until everything has been encoded.
+		if (ret != LZMA_OK) {
+			// Once everything has been encoded successfully, the
+			// return value of lzma_code() will be LZMA_STREAM_END.
+			//
+			// It is important to check for LZMA_STREAM_END. Do not
+			// assume that getting ret != LZMA_OK would mean that
+			// everything has gone well.
+			if (ret == LZMA_STREAM_END)
+				return true;
+
+			// It's not LZMA_OK nor LZMA_STREAM_END,
+			// so it must be an error code. See lzma/base.h
+			// (src/liblzma/api/lzma/base.h in the source package
+			// or e.g. /usr/include/lzma/base.h depending on the
+			// install prefix) for the list and documentation of
+			// possible values. Most values listen in lzma_ret
+			// enumeration aren't possible in this example.
+			const char *msg;
+			switch (ret) {
+			case LZMA_MEM_ERROR:
+				msg = "Memory allocation failed";
+				break;
+
+			case LZMA_DATA_ERROR:
+				// This error is returned if the compressed
+				// or uncompressed size get near 8 EiB
+				// (2^63 bytes) because that's where the .xz
+				// file format size limits currently are.
+				// That is, the possibility of this error
+				// is mostly theoretical unless you are doing
+				// something very unusual.
+				//
+				// Note that strm->total_in and strm->total_out
+				// have nothing to do with this error. Changing
+				// those variables won't increase or decrease
+				// the chance of getting this error.
+				msg = "File size limits exceeded";
+				break;
+
+			default:
+				// This is most likely LZMA_PROG_ERROR, but
+				// if this program is buggy (or liblzma has
+				// a bug), it may be e.g. LZMA_BUF_ERROR or
+				// LZMA_OPTIONS_ERROR too.
+				//
+				// It is inconvenient to have a separate
+				// error message for errors that should be
+				// impossible to occur, but knowing the error
+				// code is important for debugging. That's why
+				// it is good to print the error code at least
+				// when there is no good error message to show.
+				msg = "Unknown error, possibly a bug";
+				break;
+			}
+
+			fprintf(stderr, "Encoder error: %s (error code %u)\n",
+					msg, ret);
+			return false;
+		}
+	}
+}
+
+
+extern int
+main(int argc, char **argv)
+{
+	// Get the preset number from the command line.
+	uint32_t preset = get_preset(argc, argv);
+
+	// Initialize a lzma_stream structure. When it is allocated on stack,
+	// it is simplest to use LZMA_STREAM_INIT macro like below. When it
+	// is allocated on heap, using memset(strmptr, 0, sizeof(*strmptr))
+	// works (as long as NULL pointers are represented with zero bits
+	// as they are on practically all computers today).
+	lzma_stream strm = LZMA_STREAM_INIT;
+
+	// Initialize the encoder. If it succeeds, compress from
+	// stdin to stdout.
+	bool success = init_encoder(&strm, preset);
+	if (success)
+		success = compress(&strm, stdin, stdout);
+
+	// Free the memory allocated for the encoder. If we were encoding
+	// multiple files, this would only need to be done after the last
+	// file. See 02_decompress.c for handling of multiple files.
+	//
+	// It is OK to call lzma_end() multiple times or when it hasn't been
+	// actually used except initialized with LZMA_STREAM_INIT.
+	lzma_end(&strm);
+
+	// Close stdout to catch possible write errors that can occur
+	// when pending data is flushed from the stdio buffers.
+	if (fclose(stdout)) {
+		fprintf(stderr, "Write error: %s\n", strerror(errno));
+		success = false;
+	}
+
+	return success ? EXIT_SUCCESS : EXIT_FAILURE;
+}
diff --git a/doc/examples/02_decompress.c b/doc/examples/02_decompress.c
new file mode 100644
index 00000000..4c0f37cb
--- /dev/null
+++ b/doc/examples/02_decompress.c
@@ -0,0 +1,287 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       02_decompress.c
+/// \brief      Decompress .xz files to stdout
+///
+/// Usage:      ./02_decompress INPUT_FILES... > OUTFILE
+///
+/// Example:    ./02_decompress foo.xz bar.xz > foobar
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <lzma.h>
+
+
+static bool
+init_decoder(lzma_stream *strm)
+{
+	// Initialize a .xz decoder. The decoder supports a memory usage limit
+	// and a set of flags.
+	//
+	// The memory usage of the decompressor depends on the settings used
+	// to compress a .xz file. It can vary from less than a megabyte to
+	// a few gigabytes, but in practice (at least for now) it rarely
+	// exceeds 65 MiB because that's how much memory is required to
+	// decompress files created with "xz -9". Settings requiring more
+	// memory take extra effort to use and don't (at least for now)
+	// provide significantly better compression in most cases.
+	//
+	// Memory usage limit is useful if it is important that the
+	// decompressor won't consume gigabytes of memory. The need
+	// for limiting depends on the application. In this example,
+	// no memory usage limiting is used. This is done by setting
+	// the limit to UINT64_MAX.
+	//
+	// The .xz format allows concatenating compressed files as is:
+	//
+	//     echo foo | xz > foobar.xz
+	//     echo bar | xz >> foobar.xz
+	//
+	// When decompressing normal standalone .xz files, LZMA_CONCATENATED
+	// should always be used to support decompression of concatenated
+	// .xz files. If LZMA_CONCATENATED isn't used, the decoder will stop
+	// after the first .xz stream. This can be useful when .xz data has
+	// been embedded inside another file format.
+	//
+	// Flags other than LZMA_CONCATENATED are supported too, and can
+	// be combined with bitwise-or. See lzma/container.h
+	// (src/liblzma/api/lzma/container.h in the source package or e.g.
+	// /usr/include/lzma/container.h depending on the install prefix)
+	// for details.
+	lzma_ret ret = lzma_stream_decoder(
+			strm, UINT64_MAX, LZMA_CONCATENATED);
+
+	// Return successfully if the initialization went fine.
+	if (ret == LZMA_OK)
+		return true;
+
+	// Something went wrong. The possible errors are documented in
+	// lzma/container.h (src/liblzma/api/lzma/container.h in the source
+	// package or e.g. /usr/include/lzma/container.h depending on the
+	// install prefix).
+	//
+	// Note that LZMA_MEMLIMIT_ERROR is never possible here. If you
+	// specify a very tiny limit, the error will be delayed until
+	// the first headers have been parsed by a call to lzma_code().
+	const char *msg;
+	switch (ret) {
+	case LZMA_MEM_ERROR:
+		msg = "Memory allocation failed";
+		break;
+
+	case LZMA_OPTIONS_ERROR:
+		msg = "Unsupported decompressor flags";
+		break;
+
+	default:
+		// This is most likely LZMA_PROG_ERROR indicating a bug in
+		// this program or in liblzma. It is inconvenient to have a
+		// separate error message for errors that should be impossible
+		// to occur, but knowing the error code is important for
+		// debugging. That's why it is good to print the error code
+		// at least when there is no good error message to show.
+		msg = "Unknown error, possibly a bug";
+		break;
+	}
+
+	fprintf(stderr, "Error initializing the decoder: %s (error code %u)\n",
+			msg, ret);
+	return false;
+}
+
+
+static bool
+decompress(lzma_stream *strm, const char *inname, FILE *infile, FILE *outfile)
+{
+	// When LZMA_CONCATENATED flag was used when initializing the decoder,
+	// we need to tell lzma_code() when there will be no more input.
+	// This is done by setting action to LZMA_FINISH instead of LZMA_RUN
+	// in the same way as it is done when encoding.
+	//
+	// When LZMA_CONCATENATED isn't used, there is no need to use
+	// LZMA_FINISH to tell when all the input has been read, but it
+	// is still OK to use it if you want. When LZMA_CONCATENATED isn't
+	// used, the decoder will stop after the first .xz stream. In that
+	// case some unused data may be left in strm->next_in.
+	lzma_action action = LZMA_RUN;
+
+	uint8_t inbuf[BUFSIZ];
+	uint8_t outbuf[BUFSIZ];
+
+	strm->next_in = NULL;
+	strm->avail_in = 0;
+	strm->next_out = outbuf;
+	strm->avail_out = sizeof(outbuf);
+
+	while (true) {
+		if (strm->avail_in == 0 && !feof(infile)) {
+			strm->next_in = inbuf;
+			strm->avail_in = fread(inbuf, 1, sizeof(inbuf),
+					infile);
+
+			if (ferror(infile)) {
+				fprintf(stderr, "%s: Read error: %s\n",
+						inname, strerror(errno));
+				return false;
+			}
+
+			// Once the end of the input file has been reached,
+			// we need to tell lzma_code() that no more input
+			// will be coming. As said before, this isn't required
+			// if the LZMA_CONATENATED flag isn't used when
+			// initializing the decoder.
+			if (feof(infile))
+				action = LZMA_FINISH;
+		}
+
+		lzma_ret ret = lzma_code(strm, action);
+
+		if (strm->avail_out == 0 || ret == LZMA_STREAM_END) {
+			size_t write_size = sizeof(outbuf) - strm->avail_out;
+
+			if (fwrite(outbuf, 1, write_size, outfile)
+					!= write_size) {
+				fprintf(stderr, "Write error: %s\n",
+						strerror(errno));
+				return false;
+			}
+
+			strm->next_out = outbuf;
+			strm->avail_out = sizeof(outbuf);
+		}
+
+		if (ret != LZMA_OK) {
+			// Once everything has been decoded successfully, the
+			// return value of lzma_code() will be LZMA_STREAM_END.
+			//
+			// It is important to check for LZMA_STREAM_END. Do not
+			// assume that getting ret != LZMA_OK would mean that
+			// everything has gone well or that when you aren't
+			// getting more output it must have successfully
+			// decoded everything.
+			if (ret == LZMA_STREAM_END)
+				return true;
+
+			// It's not LZMA_OK nor LZMA_STREAM_END,
+			// so it must be an error code. See lzma/base.h
+			// (src/liblzma/api/lzma/base.h in the source package
+			// or e.g. /usr/include/lzma/base.h depending on the
+			// install prefix) for the list and documentation of
+			// possible values. Many values listen in lzma_ret
+			// enumeration aren't possible in this example, but
+			// can be made possible by enabling memory usage limit
+			// or adding flags to the decoder initialization.
+			const char *msg;
+			switch (ret) {
+			case LZMA_MEM_ERROR:
+				msg = "Memory allocation failed";
+				break;
+
+			case LZMA_FORMAT_ERROR:
+				// .xz magic bytes weren't found.
+				msg = "The input is not in the .xz format";
+				break;
+
+			case LZMA_OPTIONS_ERROR:
+				// For example, the headers specify a filter
+				// that isn't supported by this liblzma
+				// version (or it hasn't been enabled when
+				// building liblzma, but no-one sane does
+				// that unless building liblzma for an
+				// embedded system). Upgrading to a newer
+				// liblzma might help.
+				//
+				// Note that it is unlikely that the file has
+				// accidentally became corrupt if you get this
+				// error. The integrity of the .xz headers is
+				// always verified with a CRC32, so
+				// unintentionally corrupt files can be
+				// distinguished from unsupported files.
+				msg = "Unsupported compression options";
+				break;
+
+			case LZMA_DATA_ERROR:
+				msg = "Compressed file is corrupt";
+				break;
+
+			case LZMA_BUF_ERROR:
+				// Typically this error means that a valid
+				// file has got truncated, but it might also
+				// be a damaged part in the file that makes
+				// the decoder think the file is truncated.
+				// If you prefer, you can use the same error
+				// message for this as for LZMA_DATA_ERROR.
+				msg = "Compressed file is truncated or "
+						"otherwise corrupt";
+				break;
+
+			default:
+				// This is most likely LZMA_PROG_ERROR.
+				msg = "Unknown error, possibly a bug";
+				break;
+			}
+
+			fprintf(stderr, "%s: Decoder error: "
+					"%s (error code %u)\n",
+					inname, msg, ret);
+			return false;
+		}
+	}
+}
+
+
+extern int
+main(int argc, char **argv)
+{
+	if (argc <= 1) {
+		fprintf(stderr, "Usage: %s FILES...\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	lzma_stream strm = LZMA_STREAM_INIT;
+
+	bool success = true;
+
+	// Try to decompress all files.
+	for (int i = 1; i < argc; ++i) {
+		if (!init_decoder(&strm)) {
+			// Decoder initialization failed. There's no point
+			// to retry it so we need to exit.
+			success = false;
+			break;
+		}
+
+		FILE *infile = fopen(argv[i], "rb");
+
+		if (infile == NULL) {
+			fprintf(stderr, "%s: Error opening the "
+					"input file: %s\n",
+					argv[i], strerror(errno));
+			success = false;
+		} else {
+			success &= decompress(&strm, argv[i], infile, stdout);
+			fclose(infile);
+		}
+	}
+
+	// Free the memory allocated for the decoder. This only needs to be
+	// done after the last file.
+	lzma_end(&strm);
+
+	if (fclose(stdout)) {
+		fprintf(stderr, "Write error: %s\n", strerror(errno));
+		success = false;
+	}
+
+	return success ? EXIT_SUCCESS : EXIT_FAILURE;
+}
diff --git a/doc/examples/03_compress_custom.c b/doc/examples/03_compress_custom.c
new file mode 100644
index 00000000..51abbb17
--- /dev/null
+++ b/doc/examples/03_compress_custom.c
@@ -0,0 +1,193 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       03_compress_custom.c
+/// \brief      Compress in multi-call mode using x86 BCJ and LZMA2
+///
+/// Usage:      ./03_compress_custom < INFILE > OUTFILE
+///
+/// Example:    ./03_compress_custom < foo > foo.xz
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <lzma.h>
+
+
+static bool
+init_encoder(lzma_stream *strm)
+{
+	// Use the default preset (6) for LZMA2.
+	//
+	// The lzma_options_lzma structure and the lzma_lzma_preset() function
+	// are declared in lzma/lzma.h (src/liblzma/api/lzma/lzma.h in the
+	// source package or e.g. /usr/include/lzma/lzma.h depending on
+	// the install prefix).
+	lzma_options_lzma opt_lzma2;
+	if (lzma_lzma_preset(&opt_lzma2, LZMA_PRESET_DEFAULT)) {
+		// It should never fail because the default preset
+		// (and presets 0-9 optionally with LZMA_PRESET_EXTREME)
+		// are supported by all stable liblzma versions.
+		//
+		// (The encoder initialization later in this function may
+		// still fail due to unsupported preset *if* the features
+		// required by the preset have been disabled at build time,
+		// but no-one does such things except on embedded systems.)
+		fprintf(stderr, "Unsupported preset, possibly a bug\n");
+		return false;
+	}
+
+	// Now we could customize the LZMA2 options if we wanted. For example,
+	// we could set the the dictionary size (opt_lzma2.dict_size) to
+	// something else than the default (8 MiB) of the default preset.
+	// See lzma/lzma.h for details of all LZMA2 options.
+	//
+	// The x86 BCJ filter will try to modify the x86 instruction stream so
+	// that LZMA2 can compress it better. The x86 BCJ filter doesn't need
+	// any options so it will be set to NULL below.
+	//
+	// Construct the filter chain. The uncompressed data goes first to
+	// the first filter in the array, in this case the x86 BCJ filter.
+	// The array is always terminated by setting .id = LZMA_VLI_UNKNOWN.
+	//
+	// See lzma/filter.h for more information about the lzma_filter
+	// structure.
+	lzma_filter filters[] = {
+		{ .id = LZMA_FILTER_X86, .options = NULL },
+		{ .id = LZMA_FILTER_LZMA2, .options = &opt_lzma2 },
+		{ .id = LZMA_VLI_UNKNOWN, .options = NULL },
+	};
+
+	// Initialize the encoder using the custom filter chain.
+	lzma_ret ret = lzma_stream_encoder(strm, filters, LZMA_CHECK_CRC64);
+
+	if (ret == LZMA_OK)
+		return true;
+
+	const char *msg;
+	switch (ret) {
+	case LZMA_MEM_ERROR:
+		msg = "Memory allocation failed";
+		break;
+
+	case LZMA_OPTIONS_ERROR:
+		// We are no longer using a plain preset so this error
+		// message has been edited accordingly compared to
+		// 01_compress_easy.c.
+		msg = "Specified filter chain is not supported";
+		break;
+
+	case LZMA_UNSUPPORTED_CHECK:
+		msg = "Specified integrity check is not supported";
+		break;
+
+	default:
+		msg = "Unknown error, possibly a bug";
+		break;
+	}
+
+	fprintf(stderr, "Error initializing the encoder: %s (error code %u)\n",
+			msg, ret);
+	return false;
+}
+
+
+// This function is identical to the one in 01_compress_easy.c.
+static bool
+compress(lzma_stream *strm, FILE *infile, FILE *outfile)
+{
+	lzma_action action = LZMA_RUN;
+
+	uint8_t inbuf[BUFSIZ];
+	uint8_t outbuf[BUFSIZ];
+
+	strm->next_in = NULL;
+	strm->avail_in = 0;
+	strm->next_out = outbuf;
+	strm->avail_out = sizeof(outbuf);
+
+	while (true) {
+		if (strm->avail_in == 0 && !feof(infile)) {
+			strm->next_in = inbuf;
+			strm->avail_in = fread(inbuf, 1, sizeof(inbuf),
+					infile);
+
+			if (ferror(infile)) {
+				fprintf(stderr, "Read error: %s\n",
+						strerror(errno));
+				return false;
+			}
+
+			if (feof(infile))
+				action = LZMA_FINISH;
+		}
+
+		lzma_ret ret = lzma_code(strm, action);
+
+		if (strm->avail_out == 0 || ret == LZMA_STREAM_END) {
+			size_t write_size = sizeof(outbuf) - strm->avail_out;
+
+			if (fwrite(outbuf, 1, write_size, outfile)
+					!= write_size) {
+				fprintf(stderr, "Write error: %s\n",
+						strerror(errno));
+				return false;
+			}
+
+			strm->next_out = outbuf;
+			strm->avail_out = sizeof(outbuf);
+		}
+
+		if (ret != LZMA_OK) {
+			if (ret == LZMA_STREAM_END)
+				return true;
+
+			const char *msg;
+			switch (ret) {
+			case LZMA_MEM_ERROR:
+				msg = "Memory allocation failed";
+				break;
+
+			case LZMA_DATA_ERROR:
+				msg = "File size limits exceeded";
+				break;
+
+			default:
+				msg = "Unknown error, possibly a bug";
+				break;
+			}
+
+			fprintf(stderr, "Encoder error: %s (error code %u)\n",
+					msg, ret);
+			return false;
+		}
+	}
+}
+
+
+extern int
+main(void)
+{
+	lzma_stream strm = LZMA_STREAM_INIT;
+
+	bool success = init_encoder(&strm);
+	if (success)
+		success = compress(&strm, stdin, stdout);
+
+	lzma_end(&strm);
+
+	if (fclose(stdout)) {
+		fprintf(stderr, "Write error: %s\n", strerror(errno));
+		success = false;
+	}
+
+	return success ? EXIT_SUCCESS : EXIT_FAILURE;
+}
diff --git a/doc/examples/Makefile b/doc/examples/Makefile
new file mode 100644
index 00000000..644dc32e
--- /dev/null
+++ b/doc/examples/Makefile
@@ -0,0 +1,23 @@
+#
+# Author: Lasse Collin
+#
+# This file has been put into the public domain.
+# You can do whatever you want with this file.
+#
+
+CC = c99
+CFLAGS = -g
+LDFLAGS = -llzma
+
+PROGS = \
+	01_compress_easy \
+	02_decompress \
+	03_compress_custom
+
+all: $(PROGS)
+
+.c:
+	$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
+
+clean:
+	-rm -f $(PROGS)