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[core] Extract base64_decode_quad_ to deduplicate base64 decode logic

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The base64 character-to-byte conversion was duplicated in both the
main decode loop and the tail/padding path. Extract into a shared
static helper to reduce flash usage (-64 bytes on ESP32).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
J. Nick Koston
2026-02-20 00:02:27 -06:00
parent efe54e3b5e
commit 9a028f37ba
1 changed files with 14 additions and 15 deletions
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29
esphome/core/helpers.cpp
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@@ -589,10 +589,19 @@ size_t base64_decode(const std::string &encoded_string, uint8_t *buf, size_t buf
return base64_decode(reinterpret_cast<const uint8_t *>(encoded_string.data()), encoded_string.size(), buf, buf_len);
}
// Convert 4 base64 characters to 3 decoded bytes
static inline void base64_decode_quad_(uint8_t *char_array_4, uint8_t *char_array_3) {
for (int i = 0; i < 4; i++)
char_array_4[i] = base64_find_char(char_array_4[i]);
char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
}
size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *buf, size_t buf_len) {
size_t in_len = encoded_len;
int i = 0;
int j = 0;
size_t in = 0;
size_t out = 0;
uint8_t char_array_4[4], char_array_3[3];
@@ -605,12 +614,7 @@ size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *b
char_array_4[i++] = encoded_data[in];
in++;
if (i == 4) {
for (i = 0; i < 4; i++)
char_array_4[i] = base64_find_char(char_array_4[i]);
char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
base64_decode_quad_(char_array_4, char_array_3);
for (i = 0; i < 3; i++) {
if (out < buf_len) {
@@ -624,17 +628,12 @@ size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *b
}
if (i) {
for (j = i; j < 4; j++)
for (int j = i; j < 4; j++)
char_array_4[j] = 0;
for (j = 0; j < 4; j++)
char_array_4[j] = base64_find_char(char_array_4[j]);
base64_decode_quad_(char_array_4, char_array_3);
char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
for (j = 0; j < i - 1; j++) {
for (int j = 0; j < i - 1; j++) {
if (out < buf_len) {
buf[out++] = char_array_3[j];
} else {