OFHuffmanTree.h

/*
 * Copyright (c) 2008-2026 Jonathan Schleifer <js@nil.im>
 *
 * All rights reserved.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License version 3.0 only,
 * as published by the Free Software Foundation.
 *
 * 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 Lesser General Public License
 * version 3.0 for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * version 3.0 along with this program. If not, see
 * <https://www.gnu.org/licenses/>.
 */
 
#include <stdbool.h>
#include <stdint.h>
 
#import "macros.h"
 
#import "OFInvalidFormatException.h"
 
OF_ASSUME_NONNULL_BEGIN
 
typedef struct _OFHuffmanTree {
    struct _OFHuffmanTree *_Nullable leaves[2];
    uint16_t value;
} *OFHuffmanTree;
 
/* Inlined for performance. */
static OF_INLINE bool
_OFHuffmanTreeWalk(id _Nullable stream,
    bool (*bitReader)(id _Nullable, uint16_t *_Nonnull, uint8_t),
    OFHuffmanTree _Nonnull *_Nonnull tree, uint16_t *_Nonnull value)
{
    OFHuffmanTree iter = *tree;
    uint16_t bits;
 
    while (iter->value == 0xFFFF) {
        if OF_UNLIKELY (!bitReader(stream, &bits, 1)) {
            *tree = iter;
            return false;
        }
 
        if OF_UNLIKELY (iter->leaves[bits] == NULL)
            @throw [OFInvalidFormatException exception];
 
        iter = iter->leaves[bits];
    }
 
    *value = iter->value;
    return true;
}
 
#ifdef __cplusplus
extern "C" {
#endif
extern OFHuffmanTree _Nonnull _OFHuffmanTreeNew(uint8_t lengths[_Nonnull],
    uint16_t count) OF_VISIBILITY_INTERNAL;
extern OFHuffmanTree _Nonnull _OFHuffmanTreeNewSingle(uint16_t value)
    OF_VISIBILITY_INTERNAL;
extern void _OFHuffmanTreeFree(OFHuffmanTree _Nonnull tree)
    OF_VISIBILITY_INTERNAL;
#ifdef __cplusplus
}
#endif
 
OF_ASSUME_NONNULL_END