/* $NetBSD: unpack.c,v 1.3 2017/08/04 07:27:08 mrg Exp $ */
/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2009 Xin LI <delphij@FreeBSD.org>
*
* 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
*/
/* This file is #included by gzip.c */
/*
* pack(1) file format:
*
* The first 7 bytes is the header:
* 00, 01 - Signature (US, RS), we already validated it earlier.
* 02..05 - Uncompressed size
* 06 - Level for the huffman tree (<=24)
*
* pack(1) will then store symbols (leaf) nodes count in each huffman
* tree levels, each level would consume 1 byte (See [1]).
*
* After the symbol count table, there is the symbol table, storing
* symbols represented by corresponding leaf node. EOB is not being
* explicitly transmitted (not necessary anyway) in the symbol table.
*
* Compressed data goes after the symbol table.
*
* NOTES
*
* [1] If we count EOB into the symbols, that would mean that we will
* have at most 256 symbols in the huffman tree. pack(1) rejects empty
* file and files that just repeats one character, which means that we
* will have at least 2 symbols. Therefore, pack(1) would reduce the
* last level symbol count by 2 which makes it a number in
* range [0..254], so all levels' symbol count would fit into 1 byte.
*/
#define PACK_HEADER_LENGTH 7
#define HTREE_MAXLEVEL 24
/*
* unpack descriptor
*
* Represent the huffman tree in a similar way that pack(1) would
* store in a packed file. We store all symbols in a linear table,
* and store pointers to each level's first symbol. In addition to
* that, maintain two counts for each level: inner nodes count and
* leaf nodes count.
*/
typedef struct {
int symbol_size; /* Size of the symbol table */
int treelevels; /* Levels for the huffman tree */
int *symbolsin; /* Table of leaf symbols count in each
* level */
int *inodesin; /* Table of internal nodes count in
* each level */
char *symbol; /* The symbol table */
char *symbol_eob; /* Pointer to the EOB symbol */
char **tree; /* Decoding huffman tree (pointers to
* first symbol of each tree level */
off_t uncompressed_size; /* Uncompressed size */
FILE *fpIn; /* Input stream */
FILE *fpOut; /* Output stream */
} unpack_descriptor_t;
/*
* Release resource allocated to an unpack descriptor.
*
* Caller is responsible to make sure that all of these pointers are
* initialized (in our case, they all point to valid memory block).
* We don't zero out pointers here because nobody else would ever
* reference the memory block without scrubbing them.
*/
static void
unpack_descriptor_fini(unpack_descriptor_t *unpackd)
{
free(unpackd->symbolsin);
free(unpackd->inodesin);
free(unpackd->symbol);
free(unpackd->tree);
fclose(unpackd->fpIn);
fclose(unpackd->fpOut);
}
/*
* Recursively fill the internal node count table
*/
static void
unpackd_fill_inodesin(const unpack_descriptor_t *unpackd, int level)
{
/*
* The internal nodes would be 1/2 of total internal nodes and
* leaf nodes in the next level. For the last level there
* would be no internal node by definition.
*/
if (level < unpackd->treelevels) {
unpackd_fill_inodesin(unpackd, level + 1);
unpackd->inodesin[level] = (unpackd->inodesin[level + 1] +
unpackd->symbolsin[level + 1]) / 2;
} else
unpackd->inodesin[level] = 0;
}
/*
* Update counter for accepted bytes
*/
static void
accepted_bytes(off_t *bytes_in, off_t newbytes)
{
if (bytes_in != NULL)
(*bytes_in) += newbytes;
}
/*
* Read file header and construct the tree. Also, prepare the buffered I/O
* for decode routine.
*
* Return value is uncompressed size.
*/
static void
unpack_parse_header(int in, int out, char *pre, size_t prelen, off_t *bytes_in,
unpack_descriptor_t *unpackd)
{
unsigned char hdr[PACK_HEADER_LENGTH]; /* buffer for header */
ssize_t bytesread; /* Bytes read from the file */
int i, j, thisbyte;
/* Prepend the header buffer if we already read some data */
if (prelen != 0)
memcpy(hdr, pre, prelen);
/* Read in and fill the rest bytes of header */
bytesread = read(in, hdr + prelen, PACK_HEADER_LENGTH - prelen);
if (bytesread < 0)
maybe_err("Error reading pack header");
infile_newdata(bytesread);
accepted_bytes(bytes_in, PACK_HEADER_LENGTH);
/* Obtain uncompressed length (bytes 2,3,4,5) */
unpackd->uncompressed_size = 0;
for (i = 2; i <= 5; i++) {
unpackd->uncompressed_size <<= 8;
unpackd->uncompressed_size |= hdr[i];
}
/* Get the levels of the tree */
unpackd->treelevels = hdr[6];
if (unpackd->treelevels > HTREE_MAXLEVEL || unpackd->treelevels < 1)
maybe_errx("Huffman tree has insane levels");
/* Let libc take care for buffering from now on */
if ((unpackd->fpIn = fdopen(in, "r")) == NULL)
maybe_err("Can not fdopen() input stream");
if ((unpackd->fpOut = fdopen(out, "w")) == NULL)
maybe_err("Can not fdopen() output stream");
/* Allocate for the tables of bounds and the tree itself */
unpackd->inodesin =
calloc(unpackd->treelevels, sizeof(*(unpackd->inodesin)));
unpackd->symbolsin =
calloc(unpackd->treelevels, sizeof(*(unpackd->symbolsin)));
unpackd->tree =
calloc(unpackd->treelevels, (sizeof(*(unpackd->tree))));
if (unpackd->inodesin == NULL || unpackd->symbolsin == NULL ||
unpackd->tree == NULL)
maybe_err("calloc");
/* We count from 0 so adjust to match array upper bound */
unpackd->treelevels--;
/* Read the levels symbol count table and calculate total */
unpackd->symbol_size = 1; /* EOB */
for (i = 0; i <= unpackd->treelevels; i++) {
if ((thisbyte = fgetc(unpackd->fpIn)) == EOF)
maybe_err("File appears to be truncated");
unpackd->symbolsin[i] = (unsigned char)thisbyte;
unpackd->symbol_size += unpackd->symbolsin[i];
}
accepted_bytes(bytes_in, unpackd->treelevels);
if (unpackd->symbol_size > 256)
maybe_errx("Bad symbol table");
infile_newdata(unpackd->treelevels);
/* Allocate for the symbol table, point symbol_eob at the beginning */
unpackd->symbol_eob = unpackd->symbol = calloc(1, unpackd->symbol_size);
if (unpackd->symbol == NULL)
maybe_err("calloc");
/*
* Read in the symbol table, which contain [2, 256] symbols.
* In order to fit the count in one byte, pack(1) would offset
* it by reducing 2 from the actual number from the last level.
*
* We adjust the last level's symbol count by 1 here, because
* the EOB symbol is not being transmitted explicitly. Another
* adjustment would be done later afterward.
*/
unpackd->symbolsin[unpackd->treelevels]++;
for (i = 0; i <= unpackd->treelevels; i++) {
unpackd->tree[i] = unpackd->symbol_eob;
for (j = 0; j < unpackd->symbolsin[i]; j++) {
if ((thisbyte = fgetc(unpackd->fpIn)) == EOF)
maybe_errx("Symbol table truncated");
*unpackd->symbol_eob++ = (char)thisbyte;
}
infile_newdata(unpackd->symbolsin[i]);
accepted_bytes(bytes_in, unpackd->symbolsin[i]);
}
/* Now, take account for the EOB symbol as well */
unpackd->symbolsin[unpackd->treelevels]++;
/*
* The symbolsin table has been constructed now.
* Calculate the internal nodes count table based on it.
*/
unpackd_fill_inodesin(unpackd, 0);
}
/*
* Decode huffman stream, based on the huffman tree.
*/
static void
unpack_decode(const unpack_descriptor_t *unpackd, off_t *bytes_in)
{
int thislevel, thiscode, thisbyte, inlevelindex;
int i;
off_t bytes_out = 0;
const char *thissymbol; /* The symbol pointer decoded from stream */
/*
* Decode huffman. Fetch every bytes from the file, get it
* into 'thiscode' bit-by-bit, then output the symbol we got
* when one has been found.
*
* Assumption: sizeof(int) > ((max tree levels + 1) / 8).
* bad things could happen if not.
*/
thislevel = 0;
thiscode = thisbyte = 0;
while ((thisbyte = fgetc(unpackd->fpIn)) != EOF) {
accepted_bytes(bytes_in, 1);
infile_newdata(1);
check_siginfo();
/*
* Split one bit from thisbyte, from highest to lowest,
* feed the bit into thiscode, until we got a symbol from
* the tree.
*/
for (i = 7; i >= 0; i--) {
thiscode = (thiscode << 1) | ((thisbyte >> i) & 1);
/* Did we got a symbol? (referencing leaf node) */
if (thiscode >= unpackd->inodesin[thislevel]) {
inlevelindex =
thiscode - unpackd->inodesin[thislevel];
if (inlevelindex > unpackd->symbolsin[thislevel])
maybe_errx("File corrupt");
thissymbol =
&(unpackd->tree[thislevel][inlevelindex]);
if ((thissymbol == unpackd->symbol_eob) &&
(bytes_out == unpackd->uncompressed_size))
goto finished;
fputc((*thissymbol), unpackd->fpOut);
bytes_out++;
/* Prepare for next input */
thislevel = 0; thiscode = 0;
} else {
thislevel++;
if (thislevel > unpackd->treelevels)
maybe_errx("File corrupt");
}
}
}
finished:
if (bytes_out != unpackd->uncompressed_size)
maybe_errx("Premature EOF");
}
/* Handler for pack(1)'ed file */
static off_t
unpack(int in, int out, char *pre, size_t prelen, off_t *bytes_in)
{
unpack_descriptor_t unpackd;
in = dup(in);
if (in == -1)
maybe_err("dup");
out = dup(out);
if (out == -1)
maybe_err("dup");
unpack_parse_header(in, out, pre, prelen, bytes_in, &unpackd);
unpack_decode(&unpackd, bytes_in);
unpack_descriptor_fini(&unpackd);
/* If we reached here, the unpack was successful */
return (unpackd.uncompressed_size);
}
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