include: introduce byte counting functions.
This patch adds the following three functions: bits_to_bytes(bits) - the number of bytes needed to hold 'bits' bytes_to_int32(bytes) - the number of 4-byte units to hold 'bytes' pad_to_int32(bytes) - the closest multiple of 4 equal to or larger than 'bytes'. All three operations are common in protocol processing and currently the server has ((foo + 7)/8 + 3)/4 operations all over the place. A common set of functions reduce the error rate of these (albeit simple) calculations and improve readability of the code. The functions do not check for overflow. Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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@ -180,6 +180,36 @@ typedef struct _xReq *xReqPtr;
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#endif
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/**
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* Calculate the number of bytes needed to hold bits.
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* @param bits The minimum number of bits needed.
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* @return The number of bytes needed to hold bits.
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*/
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static inline int
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bits_to_bytes(const int bits) {
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return ((bits + 7) >> 3);
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}
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/**
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* Calculate the number of 4-byte units needed to hold the given number of
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* bytes.
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* @param bytes The minimum number of bytes needed.
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* @return The number of 4-byte units needed to hold bytes.
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*/
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static inline int
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bytes_to_int32(const int bytes) {
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return (((bytes) + 3) >> 2);
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}
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/**
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* Calculate the number of bytes (in multiples of 4) needed to hold bytes.
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* @param bytes The minimum number of bytes needed.
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* @return The closest multiple of 4 that is equal or higher than bytes.
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*/
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static inline int
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pad_to_int32(const int bytes) {
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return (((bytes) + 3) & ~3);
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}
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/* some macros to help swap requests, replies, and events */
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#define LengthRestB(stuff) \
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39
test/input.c
39
test/input.c
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@ -678,6 +678,44 @@ static void dix_grab_matching(void)
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g_assert(rc == TRUE);
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}
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static void include_byte_padding_macros(void)
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{
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int i;
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g_test_message("Testing bits_to_bytes()");
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/* the macros don't provide overflow protection */
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for (i = 0; i < INT_MAX - 7; i++)
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{
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int expected_bytes;
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expected_bytes = (i + 7)/8;
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g_assert(bits_to_bytes(i) >= i/8);
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g_assert((bits_to_bytes(i) * 8) - i <= 7);
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}
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g_test_message("Testing bytes_to_int32()");
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for (i = 0; i < INT_MAX - 3; i++)
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{
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int expected_4byte;
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expected_4byte = (i + 3)/4;
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g_assert(bytes_to_int32(i) <= i);
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g_assert((bytes_to_int32(i) * 4) - i <= 3);
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}
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g_test_message("Testing pad_to_int32");
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for (i = 0; i < INT_MAX - 3; i++)
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{
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int expected_bytes;
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expected_bytes = ((i + 3)/4) * 4;
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g_assert(pad_to_int32(i) >= i);
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g_assert(pad_to_int32(i) - i <= 3);
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}
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}
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int main(int argc, char** argv)
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{
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g_test_init(&argc, &argv,NULL);
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@ -688,6 +726,7 @@ int main(int argc, char** argv)
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g_test_add_func("/dix/input/check-grab-values", dix_check_grab_values);
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g_test_add_func("/dix/input/xi2-struct-sizes", xi2_struct_sizes);
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g_test_add_func("/dix/input/grab_matching", dix_grab_matching);
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g_test_add_func("/include/byte_padding_macros", include_byte_padding_macros);
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return g_test_run();
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}
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