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Make sure huffman trees always have valid symbols

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- Symbols added to the tree are valid inside HuffmanTreeBuildExplicit().
- In HuffmanTreeBuildImplicit(), make sure 'root_symbol' is
valid in case of a single symbol tree.

Change-Id: I7de5de71ff28f41e2d6228b29ed8dd4a20813e99
This commit is contained in:
Urvang Joshi 2012-05-10 11:37:17 +05:30
parent 4105061840
commit 14757f8ae2
3 changed files with 14 additions and 6 deletions
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4
src/dec/vp8l.c
View File

@ -250,8 +250,8 @@ static int ReadHuffmanCode(int alphabet_size, VP8LDecoder* const dec,
codes[1] = 1; codes[1] = 1;
code_lengths[1] = num_symbols - 1; code_lengths[1] = num_symbols - 1;
} }
ok = HuffmanTreeBuildExplicit(tree, code_lengths, codes, ok = HuffmanTreeBuildExplicit(tree, code_lengths, codes, symbols,
symbols, num_symbols); alphabet_size, num_symbols);
} else { // Decode Huffman-coded code lengths. } else { // Decode Huffman-coded code lengths.
int* code_lengths = NULL; int* code_lengths = NULL;
int i; int i;

10
src/utils/huffman.c
View File

@ -163,6 +163,11 @@ int HuffmanTreeBuildImplicit(HuffmanTree* const tree,
// Build tree. // Build tree.
if (num_symbols == 1) { // Trivial case. if (num_symbols == 1) { // Trivial case.
const int max_symbol = code_lengths_size;
if (root_symbol < 0 || root_symbol >= max_symbol) {
HuffmanTreeRelease(tree);
return 0;
}
return TreeAddSymbol(tree, root_symbol, 0, 0); return TreeAddSymbol(tree, root_symbol, 0, 0);
} else { // Normal case. } else { // Normal case.
int ok = 0; int ok = 0;
@ -195,7 +200,7 @@ int HuffmanTreeBuildImplicit(HuffmanTree* const tree,
int HuffmanTreeBuildExplicit(HuffmanTree* const tree, int HuffmanTreeBuildExplicit(HuffmanTree* const tree,
const int* const code_lengths, const int* const code_lengths,
const int* const codes, const int* const codes,
const int* const symbols, const int* const symbols, int max_symbol,
int num_symbols) { int num_symbols) {
int ok = 0; int ok = 0;
int i; int i;
@ -211,6 +216,9 @@ int HuffmanTreeBuildExplicit(HuffmanTree* const tree,
// Add symbols one-by-one. // Add symbols one-by-one.
for (i = 0; i < num_symbols; ++i) { for (i = 0; i < num_symbols; ++i) {
if (codes[i] != NON_EXISTENT_SYMBOL) { if (codes[i] != NON_EXISTENT_SYMBOL) {
if (symbols[i] < 0 || symbols[i] >= max_symbol) {
goto End;
}
if (!TreeAddSymbol(tree, symbols[i], codes[i], code_lengths[i])) { if (!TreeAddSymbol(tree, symbols[i], codes[i], code_lengths[i])) {
goto End; goto End;
} }

6
src/utils/huffman.h
View File

@ -56,12 +56,12 @@ int HuffmanTreeBuildImplicit(HuffmanTree* const tree,
int code_lengths_size); int code_lengths_size);
// Build a Huffman tree with explicitly given lists of code lengths, codes // Build a Huffman tree with explicitly given lists of code lengths, codes
// and symbols. // and symbols. Verifies that all symbols added are smaller than max_symbol.
// Returns false in case of error (invalid tree or memory error). // Returns false in case of an invalid symbol, invalid tree or memory error.
int HuffmanTreeBuildExplicit(HuffmanTree* const tree, int HuffmanTreeBuildExplicit(HuffmanTree* const tree,
const int* const code_lengths, const int* const code_lengths,
const int* const codes, const int* const codes,
const int* const symbols, const int* const symbols, int max_symbol,
int num_symbols); int num_symbols);
// Utility: converts Huffman code lengths to corresponding Huffman codes. // Utility: converts Huffman code lengths to corresponding Huffman codes.