Add an unpatched version of xz, XZ Utils, to /trunk/deps/third_party

xz/src/liblzma/common/vli_decoder.c

+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       vli_decoder.c
+/// \brief      Decodes variable-length integers
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "common.h"
+
+
+extern LZMA_API(lzma_ret)
+lzma_vli_decode(lzma_vli *restrict vli, size_t *vli_pos,
+                const uint8_t *restrict in, size_t *restrict in_pos,
+                size_t in_size)
+{
+        // If we haven't been given vli_pos, work in single-call mode.
+        size_t vli_pos_internal = 0;
+        if (vli_pos == NULL) {
+                vli_pos = &vli_pos_internal;
+                *vli = 0;
+
+                // If there's no input, use LZMA_DATA_ERROR. This way it is
+                // easy to decode VLIs from buffers that have known size,
+                // and get the correct error code in case the buffer is
+                // too short.
+                if (*in_pos >= in_size)
+                        return LZMA_DATA_ERROR;
+
+        } else {
+                // Initialize *vli when starting to decode a new integer.
+                if (*vli_pos == 0)
+                        *vli = 0;
+
+                // Validate the arguments.
+                if (*vli_pos >= LZMA_VLI_BYTES_MAX
+                                || (*vli >> (*vli_pos * 7)) != 0)
+                        return LZMA_PROG_ERROR;;
+
+                if (*in_pos >= in_size)
+                        return LZMA_BUF_ERROR;
+        }
+
+        do {
+                // Read the next byte. Use a temporary variable so that we
+                // can update *in_pos immediately.
+                const uint8_t byte = in[*in_pos];
+                ++*in_pos;
+
+                // Add the newly read byte to *vli.
+                *vli += (lzma_vli)(byte & 0x7F) << (*vli_pos * 7);
+                ++*vli_pos;
+
+                // Check if this is the last byte of a multibyte integer.
+                if ((byte & 0x80) == 0) {
+                        // We don't allow using variable-length integers as
+                        // padding i.e. the encoding must use the most the
+                        // compact form.
+                        if (byte == 0x00 && *vli_pos > 1)
+                                return LZMA_DATA_ERROR;
+
+                        return vli_pos == &vli_pos_internal
+                                        ? LZMA_OK : LZMA_STREAM_END;
+                }
+
+                // There is at least one more byte coming. If we have already
+                // read maximum number of bytes, the integer is considered
+                // corrupt.
+                //
+                // If we need bigger integers in future, old versions liblzma
+                // will confusingly indicate the file being corrupt istead of
+                // unsupported. I suppose it's still better this way, because
+                // in the foreseeable future (writing this in 2008) the only
+                // reason why files would appear having over 63-bit integers
+                // is that the files are simply corrupt.
+                if (*vli_pos == LZMA_VLI_BYTES_MAX)
+                        return LZMA_DATA_ERROR;
+
+        } while (*in_pos < in_size);
+
+        return vli_pos == &vli_pos_internal ? LZMA_DATA_ERROR : LZMA_OK;
+}