345 lines
16 KiB
C
345 lines
16 KiB
C
/* -*- tab-width: 4; -*- */
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/* vi: set sw=2 ts=4 expandtab: */
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/* Copyright 2019-2020 The Khronos Group Inc.
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* SPDX-License-Identifier: Apache-2.0
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*/
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/**
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* @file
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* @~English
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* @brief Utility for interpreting a data format descriptor.
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* @author Andrew Garrard
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*/
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#include <stdint.h>
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#include <stdio.h>
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#include <KHR/khr_df.h>
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#include "dfd.h"
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/**
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* @~English
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* @brief Interpret a Data Format Descriptor for a simple format.
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*
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* @param DFD Pointer to a Data Format Descriptor to interpret,
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described as 32-bit words in native endianness.
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Note that this is the whole descriptor, not just
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the basic descriptor block.
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* @param R Information about the decoded red channel, if any.
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* @param G Information about the decoded green channel, if any.
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* @param B Information about the decoded blue channel, if any.
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* @param A Information about the decoded alpha channel, if any.
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* @param wordBytes Byte size of the channels (unpacked) or total size (packed).
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*
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* @return An enumerant describing the decoded value,
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* or an error code in case of failure.
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**/
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enum InterpretDFDResult interpretDFD(const uint32_t *DFD,
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InterpretedDFDChannel *R,
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InterpretedDFDChannel *G,
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InterpretedDFDChannel *B,
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InterpretedDFDChannel *A,
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uint32_t *wordBytes)
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{
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/* We specifically handle "simple" cases that can be translated */
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/* to things a GPU can access. For simplicity, we also ignore */
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/* the compressed formats, which are generally a single sample */
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/* (and I believe are all defined to be little-endian in their */
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/* in-memory layout, even if some documentation confuses this). */
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/* We also just worry about layout and ignore sRGB, since that's */
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/* trivial to extract anyway. */
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/* DFD points to the whole descriptor, not the basic descriptor block. */
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/* Make everything else relative to the basic descriptor block. */
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const uint32_t *BDFDB = DFD+1;
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uint32_t numSamples = KHR_DFDSAMPLECOUNT(BDFDB);
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uint32_t sampleCounter;
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int determinedEndianness = 0;
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int determinedNormalizedness = 0;
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int determinedSignedness = 0;
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int determinedFloatness = 0;
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enum InterpretDFDResult result = 0; /* Build this up incrementally. */
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/* Clear these so following code doesn't get confused. */
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R->offset = R->size = 0;
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G->offset = G->size = 0;
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B->offset = B->size = 0;
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A->offset = A->size = 0;
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/* First rule out the multiple planes case (trivially) */
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/* - that is, we check that only bytesPlane0 is non-zero. */
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/* This means we don't handle YUV even if the API could. */
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/* (We rely on KHR_DF_WORD_BYTESPLANE0..3 being the same and */
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/* KHR_DF_WORD_BYTESPLANE4..7 being the same as a short cut.) */
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if ((BDFDB[KHR_DF_WORD_BYTESPLANE0] & ~KHR_DF_MASK_BYTESPLANE0)
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|| BDFDB[KHR_DF_WORD_BYTESPLANE4]) return i_UNSUPPORTED_MULTIPLE_PLANES;
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/* Only support the RGB color model. */
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/* We could expand this to allow "UNSPECIFIED" as well. */
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if (KHR_DFDVAL(BDFDB, MODEL) != KHR_DF_MODEL_RGBSDA) return i_UNSUPPORTED_CHANNEL_TYPES;
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/* We only pay attention to sRGB. */
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if (KHR_DFDVAL(BDFDB, TRANSFER) == KHR_DF_TRANSFER_SRGB) result |= i_SRGB_FORMAT_BIT;
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/* We only support samples at coordinate 0,0,0,0. */
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/* (We could confirm this from texel_block_dimensions in 1.2, but */
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/* the interpretation might change in later versions.) */
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for (sampleCounter = 0; sampleCounter < numSamples; ++sampleCounter) {
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if (KHR_DFDSVAL(BDFDB, sampleCounter, SAMPLEPOSITION_ALL))
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return i_UNSUPPORTED_MULTIPLE_SAMPLE_LOCATIONS;
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}
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/* Set flags and check for consistency. */
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for (sampleCounter = 0; sampleCounter < numSamples; ++sampleCounter) {
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/* Note: We're ignoring 9995, which is weird and worth special-casing */
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/* rather than trying to generalise to all float formats. */
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if (!determinedFloatness) {
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if (KHR_DFDSVAL(BDFDB, sampleCounter, QUALIFIERS)
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& KHR_DF_SAMPLE_DATATYPE_FLOAT) {
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result |= i_FLOAT_FORMAT_BIT;
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determinedFloatness = 1;
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}
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} else {
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/* Check whether we disagree with our predetermined floatness. */
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/* Note that this could justifiably happen with (say) D24S8. */
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if (KHR_DFDSVAL(BDFDB, sampleCounter, QUALIFIERS)
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& KHR_DF_SAMPLE_DATATYPE_FLOAT) {
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if (!(result & i_FLOAT_FORMAT_BIT)) return i_UNSUPPORTED_MIXED_CHANNELS;
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} else {
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if ((result & i_FLOAT_FORMAT_BIT)) return i_UNSUPPORTED_MIXED_CHANNELS;
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}
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}
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if (!determinedSignedness) {
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if (KHR_DFDSVAL(BDFDB, sampleCounter, QUALIFIERS)
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& KHR_DF_SAMPLE_DATATYPE_SIGNED) {
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result |= i_SIGNED_FORMAT_BIT;
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determinedSignedness = 1;
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}
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} else {
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/* Check whether we disagree with our predetermined signedness. */
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if (KHR_DFDSVAL(BDFDB, sampleCounter, QUALIFIERS)
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& KHR_DF_SAMPLE_DATATYPE_SIGNED) {
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if (!(result & i_SIGNED_FORMAT_BIT)) return i_UNSUPPORTED_MIXED_CHANNELS;
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} else {
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if ((result & i_SIGNED_FORMAT_BIT)) return i_UNSUPPORTED_MIXED_CHANNELS;
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}
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}
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/* We define "unnormalized" as "sample_upper = 1". */
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/* We don't check whether any non-1 normalization value is correct */
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/* (i.e. set to the maximum bit value, and check min value) on */
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/* the assumption that we're looking at a format which *came* from */
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/* an API we can support. */
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if (!determinedNormalizedness) {
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/* The ambiguity here is if the bottom bit is a single-bit value, */
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/* as in RGBA 5:5:5:1, so we defer the decision if the channel only has one bit. */
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if (KHR_DFDSVAL(BDFDB, sampleCounter, BITLENGTH) > 0) {
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if ((result & i_FLOAT_FORMAT_BIT)) {
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if (*(float *)(void *)&BDFDB[KHR_DF_WORD_SAMPLESTART +
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KHR_DF_WORD_SAMPLEWORDS * sampleCounter +
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KHR_DF_SAMPLEWORD_SAMPLEUPPER] != 1.0f) {
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result |= i_NORMALIZED_FORMAT_BIT;
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}
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} else {
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if (KHR_DFDSVAL(BDFDB, sampleCounter, SAMPLEUPPER) != 1U) {
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result |= i_NORMALIZED_FORMAT_BIT;
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}
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}
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determinedNormalizedness = 1;
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}
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}
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/* Note: We don't check for inconsistent normalization, because */
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/* channels composed of multiple samples will have 0 in the */
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/* lower/upper range. */
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/* This heuristic should handle 64-bit integers, too. */
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}
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/* If this is a packed format, we work out our offsets differently. */
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/* We assume a packed format has channels that aren't byte-aligned. */
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/* If we have a format in which every channel is byte-aligned *and* packed, */
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/* we have the RGBA/ABGR ambiguity; we *probably* don't want the packed */
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/* version in this case, and if hardware has to pack it and swizzle, */
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/* that's up to the hardware to special-case. */
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for (sampleCounter = 0; sampleCounter < numSamples; ++sampleCounter) {
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if (KHR_DFDSVAL(BDFDB, sampleCounter, BITOFFSET) & 0x7U) {
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result |= i_PACKED_FORMAT_BIT;
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/* Once we're packed, we're packed, no need to keep checking. */
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break;
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}
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}
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/* Remember: the canonical ordering of samples is to start with */
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/* the lowest bit of the channel/location which touches bit 0 of */
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/* the data, when the latter is concatenated in little-endian order, */
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/* and then progress until all the bits of that channel/location */
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/* have been processed. Multiple channels sharing the same source */
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/* bits are processed in channel ID order. (I should clarify this */
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/* for partially-shared data, but it doesn't really matter so long */
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/* as everything is consecutive, except to make things canonical.) */
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/* Note: For standard formats we could determine big/little-endianness */
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/* simply from whether the first sample starts in bit 0; technically */
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/* it's possible to have a format with unaligned channels wherein the */
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/* first channel starts at bit 0 and is one byte, yet other channels */
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/* take more bytes or aren't aligned (e.g. D24S8), but this should be */
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/* irrelevant for the formats that we support. */
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if ((result & i_PACKED_FORMAT_BIT)) {
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/* A packed format. */
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uint32_t currentChannel = ~0U; /* Don't start matched. */
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uint32_t currentBitOffset = 0;
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uint32_t currentByteOffset = 0;
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uint32_t currentBitLength = 0;
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*wordBytes = (BDFDB[KHR_DF_WORD_BYTESPLANE0] & 0xFFU);
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for (sampleCounter = 0; sampleCounter < numSamples; ++sampleCounter) {
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uint32_t sampleBitOffset = KHR_DFDSVAL(BDFDB, sampleCounter, BITOFFSET);
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uint32_t sampleByteOffset = sampleBitOffset >> 3U;
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/* The sample bitLength field stores the bit length - 1. */
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uint32_t sampleBitLength = KHR_DFDSVAL(BDFDB, sampleCounter, BITLENGTH) + 1;
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uint32_t sampleChannel = KHR_DFDSVAL(BDFDB, sampleCounter, CHANNELID);
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InterpretedDFDChannel *sampleChannelPtr;
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switch (sampleChannel) {
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case KHR_DF_CHANNEL_RGBSDA_RED:
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sampleChannelPtr = R;
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break;
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case KHR_DF_CHANNEL_RGBSDA_GREEN:
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sampleChannelPtr = G;
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break;
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case KHR_DF_CHANNEL_RGBSDA_BLUE:
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sampleChannelPtr = B;
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break;
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case KHR_DF_CHANNEL_RGBSDA_ALPHA:
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sampleChannelPtr = A;
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break;
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default:
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return i_UNSUPPORTED_CHANNEL_TYPES;
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}
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if (sampleChannel == currentChannel) {
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/* Continuation of the same channel. */
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/* Since a big (>32-bit) channel isn't "packed", */
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/* this should only happen in big-endian, or if */
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/* we have a wacky format that we won't support. */
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if (sampleByteOffset == currentByteOffset - 1U && /* One byte earlier */
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((currentBitOffset + currentBitLength) & 7U) == 0 && /* Already at the end of a byte */
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(sampleBitOffset & 7U) == 0) { /* Start at the beginning of the byte */
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/* All is good, continue big-endian. */
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/* N.B. We shouldn't be here if we decided we were little-endian, */
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/* so we don't bother to check that disagreement. */
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result |= i_BIG_ENDIAN_FORMAT_BIT;
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determinedEndianness = 1;
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} else {
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/* Oh dear. */
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/* We could be little-endian, but not with any standard format. */
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/* More likely we've got something weird that we can't support. */
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return i_UNSUPPORTED_NONTRIVIAL_ENDIANNESS;
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}
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/* Remember where we are. */
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currentBitOffset = sampleBitOffset;
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currentByteOffset = sampleByteOffset;
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currentBitLength = sampleBitLength;
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/* Accumulate the bit length. */
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sampleChannelPtr->size += sampleBitLength;
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} else {
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/* Everything is new. Hopefully. */
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currentChannel = sampleChannel;
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currentBitOffset = sampleBitOffset;
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currentByteOffset = sampleByteOffset;
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currentBitLength = sampleBitLength;
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if (sampleChannelPtr->size) {
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/* Uh-oh, we've seen this channel before. */
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return i_UNSUPPORTED_NONTRIVIAL_ENDIANNESS;
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}
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/* For now, record the bit offset in little-endian terms, */
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/* because we may not know to reverse it yet. */
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sampleChannelPtr->offset = sampleBitOffset;
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sampleChannelPtr->size = sampleBitLength;
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}
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}
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if ((result & i_BIG_ENDIAN_FORMAT_BIT)) {
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/* Our bit offsets to bit 0 of each channel are in little-endian terms. */
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/* We need to do a byte swap to work out where they should be. */
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/* We assume, for sanity, that byte sizes are a power of two for this. */
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uint32_t offsetMask = (*wordBytes - 1U) << 3U;
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R->offset ^= offsetMask;
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G->offset ^= offsetMask;
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B->offset ^= offsetMask;
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A->offset ^= offsetMask;
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}
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} else {
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/* Not a packed format. */
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/* Everything is byte-aligned. */
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/* Question is whether there multiple samples per channel. */
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uint32_t currentChannel = ~0U; /* Don't start matched. */
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uint32_t currentByteOffset = 0;
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uint32_t currentByteLength = 0;
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for (sampleCounter = 0; sampleCounter < numSamples; ++sampleCounter) {
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uint32_t sampleByteOffset = KHR_DFDSVAL(BDFDB, sampleCounter, BITOFFSET) >> 3U;
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uint32_t sampleByteLength = (KHR_DFDSVAL(BDFDB, sampleCounter, BITLENGTH) + 1) >> 3U;
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uint32_t sampleChannel = KHR_DFDSVAL(BDFDB, sampleCounter, CHANNELID);
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InterpretedDFDChannel *sampleChannelPtr;
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switch (sampleChannel) {
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case KHR_DF_CHANNEL_RGBSDA_RED:
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sampleChannelPtr = R;
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break;
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case KHR_DF_CHANNEL_RGBSDA_GREEN:
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sampleChannelPtr = G;
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break;
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case KHR_DF_CHANNEL_RGBSDA_BLUE:
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sampleChannelPtr = B;
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break;
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case KHR_DF_CHANNEL_RGBSDA_ALPHA:
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sampleChannelPtr = A;
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break;
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default:
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return i_UNSUPPORTED_CHANNEL_TYPES;
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}
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if (sampleChannel == currentChannel) {
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/* Continuation of the same channel. */
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/* Either big-endian, or little-endian with a very large channel. */
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if (sampleByteOffset == currentByteOffset - 1) { /* One byte earlier */
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if (determinedEndianness && !(result & i_BIG_ENDIAN_FORMAT_BIT)) {
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return i_UNSUPPORTED_NONTRIVIAL_ENDIANNESS;
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}
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/* All is good, continue big-endian. */
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result |= i_BIG_ENDIAN_FORMAT_BIT;
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determinedEndianness = 1;
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/* Update the start */
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sampleChannelPtr->offset = sampleByteOffset;
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} else if (sampleByteOffset == currentByteOffset + currentByteLength) {
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if (determinedEndianness && (result & i_BIG_ENDIAN_FORMAT_BIT)) {
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return i_UNSUPPORTED_NONTRIVIAL_ENDIANNESS;
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}
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/* All is good, continue little-endian. */
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determinedEndianness = 1;
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} else {
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/* Oh dear. */
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/* We could be little-endian, but not with any standard format. */
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/* More likely we've got something weird that we can't support. */
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return i_UNSUPPORTED_NONTRIVIAL_ENDIANNESS;
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}
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/* Remember where we are. */
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currentByteOffset = sampleByteOffset;
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currentByteLength = sampleByteLength;
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/* Accumulate the byte length. */
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sampleChannelPtr->size += sampleByteLength;
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/* Assume these are all the same. */
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*wordBytes = sampleChannelPtr->size;
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} else {
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/* Everything is new. Hopefully. */
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currentChannel = sampleChannel;
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currentByteOffset = sampleByteOffset;
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currentByteLength = sampleByteLength;
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if (sampleChannelPtr->size) {
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/* Uh-oh, we've seen this channel before. */
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return i_UNSUPPORTED_NONTRIVIAL_ENDIANNESS;
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}
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/* For now, record the byte offset in little-endian terms, */
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/* because we may not know to reverse it yet. */
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sampleChannelPtr->offset = sampleByteOffset;
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sampleChannelPtr->size = sampleByteLength;
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/* Assume these are all the same. */
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*wordBytes = sampleByteLength;
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}
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}
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}
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return result;
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}
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