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Code Issues Releases Activity

More efficient/compact calculations for encoded sizes.

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encodeToStrSizeBase64() is definitely more efficient (pulled from the PostgreSQL implementation).

encodeToStrSizeBase64Url() is probably about as efficient as the prior implementation but is certainly more compact.

Also add tests for zero byte encoding sizes.
This commit is contained in:
David Steele 2023-10-18 18:14:32 -04:00
parent 21c8c8a66c
commit 459d59615a
2 changed files with 8 additions and 31 deletions
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35
src/common/encode.c
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@ -86,15 +86,8 @@ encodeToStrSizeBase64(size_t sourceSize)
FUNCTION_TEST_PARAM(SIZE, sourceSize);
FUNCTION_TEST_END();
// Calculate how many groups of three are in the source
size_t encodeGroupTotal = sourceSize / 3;
// Increase by one if there is a partial group
if (sourceSize % 3 != 0)
encodeGroupTotal++;
// Four characters are needed to encode each group
FUNCTION_TEST_RETURN(SIZE, encodeGroupTotal * 4);
// Four characters are needed to encode each 3 byte group (plus up to two bytes of padding)
FUNCTION_TEST_RETURN(SIZE, (sourceSize + 2) / 3 * 4);
}
/**********************************************************************************************************************************/
@ -291,28 +284,8 @@ encodeToStrSizeBase64Url(size_t sourceSize)
FUNCTION_TEST_PARAM(SIZE, sourceSize);
FUNCTION_TEST_END();
// Calculate how many groups of three are in the source. Each group of three is encoded with four bytes.
size_t encodeTotal = sourceSize / 3 * 4;
// Determine additional required bytes for the partial group, if any
switch (sourceSize % 3)
{
// One byte requires two characters to encode
case 1:
encodeTotal += 2;
break;
// Two bytes require three characters to encode
case 2:
encodeTotal += 3;
break;
// If mod is zero then sourceSize was evenly divisible and no additional bytes are required
case 0:
break;
}
FUNCTION_TEST_RETURN(SIZE, encodeTotal);
// Four characters are needed to encode each 3 byte group, three characters for 2 bytes, and two characters for 1 byte
FUNCTION_TEST_RETURN(SIZE, sourceSize / 3 * 4 + (sourceSize % 3 == 0 ? 0 : sourceSize % 3 + 1));
}
/***********************************************************************************************************************************

4
test/src/module/common/encodeTest.c
View File

@ -16,6 +16,8 @@ testRun(void)
const unsigned char *encode = (const unsigned char *)"string_to_encode\r\n";
char destinationEncode[256];
TEST_RESULT_UINT(encodeToStrSize(encodingBase64, 0), 0, "check zero size");
encodeToStr(encodingBase64, encode, 1, destinationEncode);
TEST_RESULT_Z(destinationEncode, "cw==", "1 character encode");
TEST_RESULT_UINT(encodeToStrSize(encodingBase64, 1), strlen(destinationEncode), "check size");
@ -106,6 +108,8 @@ testRun(void)
const unsigned char *encode = (const unsigned char *)"string_to_encode\r\n";
char destinationEncode[256];
TEST_RESULT_UINT(encodeToStrSize(encodingBase64Url, 0), 0, "check zero size");
encodeToStr(encodingBase64Url, encode, 1, destinationEncode);
TEST_RESULT_Z(destinationEncode, "cw", "1 character encode");
TEST_RESULT_UINT(encodeToStrSize(encodingBase64Url, 1), strlen(destinationEncode), "check size");