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public: add swaplib
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Alibek Omarov
127
public/swaplib.h
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127
public/swaplib.h
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@@ -0,0 +1,127 @@
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/*
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swaplib.h - byte-swapping for on-disk structures
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Copyright (C) 2026 Alibek Omarov
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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*/
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#ifndef SWAPLIB_H
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#define SWAPLIB_H
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#include "build.h"
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#include "xash3d_types.h"
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typedef struct swap_struct_def_s
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{
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uint32_t offset;
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int32_t size;
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struct swap_struct_def_s *subdef;
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uint32_t count;
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uint32_t stride;
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} swap_struct_def_t;
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static inline void swap_two_bytes_( byte *a, byte *b )
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{
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byte tmp = *a;
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*a = *b;
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*b = tmp;
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}
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static inline void swap_field_( byte *p, int32_t size )
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{
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switch( size )
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{
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case 2:
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swap_two_bytes_( &p[0], &p[1] );
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break;
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case 4:
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swap_two_bytes_( &p[0], &p[3] );
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swap_two_bytes_( &p[1], &p[2] );
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break;
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case 8:
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swap_two_bytes_( &p[0], &p[7] );
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swap_two_bytes_( &p[1], &p[6] );
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swap_two_bytes_( &p[2], &p[5] );
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swap_two_bytes_( &p[3], &p[4] );
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break;
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default:
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break;
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}
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}
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static inline void swap_struct_( const swap_struct_def_t *def, size_t len, byte *data )
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{
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for( size_t i = 0; i < len; i++ )
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{
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if( def[i].size < 0 )
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{
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uint32_t count = def[i].count ? def[i].count : 1;
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for( uint32_t j = 0; j < count; j++ )
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swap_struct_( def[i].subdef, -def[i].size, &data[def[i].offset + j * def[i].stride] );
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continue;
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}
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if( def[i].count > 0 )
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{
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for( uint32_t j = 0; j < def[i].count; j++ )
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swap_field_( &data[def[i].offset + j * def[i].stride], def[i].size );
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continue;
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}
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swap_field_( &data[def[i].offset], def[i].size );
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}
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}
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#define swap_struct( swapdef, ptr ) swap_struct_(( swapdef ), sizeof( swapdef ) / sizeof( swapdef[0] ), (byte *)( ptr ))
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#define swap_struct_begin( swapdef ) static swap_struct_def_t swapdef[] = {
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#define swap_struct_field( record, field ) { .offset = offsetof( record, field ), .size = sizeof(((record *)0)->field) },
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#define swap_struct_child( record, field, child ) { .offset = offsetof( record, field ), .size = -(int32_t)(sizeof( child ) / sizeof( child[0] )), .subdef = child },
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#define swap_struct_array( record, field, cnt ) { .offset = offsetof( record, field ), .size = sizeof(((record *)0)->field[0]), .count = cnt, .stride = sizeof(((record *)0)->field[0]) },
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#define swap_struct_array_child( record, field, child, cnt ) { .offset = offsetof( record, field ), .size = -(int32_t)(sizeof( child ) / sizeof( child[0] )), .subdef = child, .count = cnt, .stride = sizeof(((record *)0)->field[0]) },
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#define swap_struct_end() }
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// this is done in macros so we can completely avoid defining this
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// in little endian targets
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#ifdef XASH_LITTLE_ENDIAN
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#define be_struct_begin( x ) swap_struct_begin( x )
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#define be_struct_field( x, y ) swap_struct_field( x, y )
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#define be_struct_child( x, y, z ) swap_struct_child( x, y, z )
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#define be_struct_array( x, y, z ) swap_struct_array( x, y, z )
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#define be_struct_array_child( x, y, z, w ) swap_struct_array_child( x, y, z, w )
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#define be_struct_end() swap_struct_end()
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#define be_struct_swap( x, y ) swap_struct( x, y )
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#define le_struct_begin( x )
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#define le_struct_field( x, y )
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#define le_struct_child( x, y, z )
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#define le_struct_array( x, y, z )
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#define le_struct_array_child( x, y, z, w )
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#define le_struct_end()
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#define le_struct_swap( x, y ) (void)(y)
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#else
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#define le_struct_begin( x ) swap_struct_begin( x )
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#define le_struct_field( x, y ) swap_struct_field( x, y )
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#define le_struct_child( x, y, z ) swap_struct_child( x, y, z )
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#define le_struct_array( x, y, z ) swap_struct_array( x, y, z )
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#define le_struct_array_child( x, y, z, w ) swap_struct_array_child( x, y, z, w )
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#define le_struct_end() swap_struct_end()
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#define le_struct_swap( x, y ) swap_struct( x, y )
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#define be_struct_begin( x )
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#define be_struct_field( x, y )
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#define be_struct_child( x, y, z )
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#define be_struct_array( x, y, z )
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#define be_struct_array_child( x, y, z, w )
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#define be_struct_end()
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#define be_struct_swap( x, y ) (void)(y)
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#endif
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#endif // SWAPLIB_H
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235
public/tests/test_swapstruct.c
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235
public/tests/test_swapstruct.c
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@@ -0,0 +1,235 @@
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#include <stddef.h>
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#include "swaplib.h"
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typedef struct
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{
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uint16_t x;
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uint16_t y;
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} inner_t;
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typedef struct
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{
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uint8_t a;
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uint16_t b;
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uint32_t c;
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inner_t inner;
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} outer_t;
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swap_struct_begin( inner_def )
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swap_struct_field( inner_t, x )
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swap_struct_field( inner_t, y )
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swap_struct_end();
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swap_struct_begin( outer_def )
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swap_struct_field( outer_t, b )
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swap_struct_field( outer_t, c )
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swap_struct_child( outer_t, inner, inner_def )
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swap_struct_end();
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typedef struct
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{
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uint32_t version;
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inner_t items[4];
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} array_outer_t;
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swap_struct_begin( array_outer_def )
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swap_struct_field( array_outer_t, version )
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swap_struct_array_child( array_outer_t, items, inner_def, 4 )
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swap_struct_end();
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typedef struct
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{
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uint16_t tag;
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uint32_t values[3];
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} int_array_t;
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swap_struct_begin( int_array_def )
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swap_struct_field( int_array_t, tag )
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swap_struct_array( int_array_t, values, 3 )
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swap_struct_end();
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static int Test_SwapField( void )
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{
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inner_t data = { .x = 0x0102, .y = 0x0304 };
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swap_struct( inner_def, &data );
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if( data.x != 0x0201 )
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return 1;
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if( data.y != 0x0403 )
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return 2;
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// swap again, should restore original
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swap_struct( inner_def, &data );
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if( data.x != 0x0102 )
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return 3;
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if( data.y != 0x0304 )
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return 4;
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return 0;
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}
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static int Test_SwapChild( void )
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{
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outer_t data =
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{
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.a = 0xAA,
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.b = 0x0102,
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.c = 0x01020304,
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.inner = { .x = 0x0506, .y = 0x0708 },
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};
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swap_struct( outer_def, &data );
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// a is uint8_t, must be untouched
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if( data.a != 0xAA )
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return 1;
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// b must be byte-swapped
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if( data.b != 0x0201 )
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return 2;
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// c must be byte-swapped
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if( data.c != 0x04030201 )
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return 3;
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// child fields must be byte-swapped
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if( data.inner.x != 0x0605 )
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return 4;
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if( data.inner.y != 0x0807 )
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return 5;
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// swap back
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swap_struct( outer_def, &data );
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if( data.b != 0x0102 )
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return 6;
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if( data.c != 0x01020304 )
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return 7;
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if( data.inner.x != 0x0506 )
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return 8;
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if( data.inner.y != 0x0708 )
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return 9;
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return 0;
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}
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static int Test_SwapArrayChild( void )
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{
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array_outer_t data =
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{
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.version = 0x01020304,
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.items =
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{
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{ .x = 0x0102, .y = 0x0304 },
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{ .x = 0x0506, .y = 0x0708 },
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{ .x = 0x090A, .y = 0x0B0C },
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{ .x = 0x0D0E, .y = 0x0F10 },
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},
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};
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swap_struct( array_outer_def, &data );
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if( data.version != 0x04030201 )
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return 1;
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if( data.items[0].x != 0x0201 || data.items[0].y != 0x0403 )
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return 2;
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if( data.items[1].x != 0x0605 || data.items[1].y != 0x0807 )
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return 3;
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if( data.items[2].x != 0x0A09 || data.items[2].y != 0x0C0B )
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return 4;
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if( data.items[3].x != 0x0E0D || data.items[3].y != 0x100F )
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return 5;
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// swap back
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swap_struct( array_outer_def, &data );
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if( data.version != 0x01020304 )
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return 6;
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if( data.items[0].x != 0x0102 || data.items[0].y != 0x0304 )
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return 7;
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if( data.items[3].x != 0x0D0E || data.items[3].y != 0x0F10 )
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return 8;
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return 0;
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}
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static int Test_SwapArray( void )
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{
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int_array_t data =
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{
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.tag = 0x0102,
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.values = { 0x01020304, 0x05060708, 0x090A0B0C },
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};
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swap_struct( int_array_def, &data );
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if( data.tag != 0x0201 )
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return 1;
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if( data.values[0] != 0x04030201 )
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return 2;
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if( data.values[1] != 0x08070605 )
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return 3;
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if( data.values[2] != 0x0C0B0A09 )
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return 4;
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// swap back
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swap_struct( int_array_def, &data );
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if( data.tag != 0x0102 )
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return 5;
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if( data.values[0] != 0x01020304 )
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return 6;
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if( data.values[1] != 0x05060708 )
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return 7;
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if( data.values[2] != 0x090A0B0C )
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return 8;
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return 0;
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}
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int main( void )
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{
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int ret;
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ret = Test_SwapField();
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if( ret > 0 )
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return ret;
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ret = Test_SwapChild();
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if( ret > 0 )
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return ret + 32;
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ret = Test_SwapArrayChild();
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if( ret > 0 )
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return ret + 64;
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ret = Test_SwapArray();
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if( ret > 0 )
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return ret + 96;
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return 0;
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}
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@@ -158,6 +158,7 @@ def build(bld):
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'atoi': 'tests/test_atoi.c',
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'parsefile': 'tests/test_parsefile.c',
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'atlas': 'tests/test_atlas.c',
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'swapstruct': 'tests/test_swapstruct.c',
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}
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for i in tests:
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