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[core] Store BASE64 chars in flash memory array

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J. Nick Koston
2025-09-07 08:56:44 -05:00
parent c33bb3a8a9
commit 960a65e2f3
1 changed files with 7 additions and 6 deletions
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13
esphome/core/helpers.cpp
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@@ -373,10 +373,11 @@ int8_t step_to_accuracy_decimals(float step) {
return str.length() - dot_pos - 1; return str.length() - dot_pos - 1;
} }
// Use C-style string constant to store in ROM instead of RAM (saves 24 bytes) // Store BASE64 characters as array - automatically placed in flash/ROM on embedded platforms
static constexpr const char *BASE64_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" static const char BASE64_CHARS[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
"abcdefghijklmnopqrstuvwxyz" 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
"0123456789+/"; 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};
// Helper function to find the index of a base64 character in the lookup table. // Helper function to find the index of a base64 character in the lookup table.
// Returns the character's position (0-63) if found, or 0 if not found. // Returns the character's position (0-63) if found, or 0 if not found.
@@ -386,8 +387,8 @@ static constexpr const char *BASE64_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
// stops processing at the first invalid character due to the is_base64() check in its // stops processing at the first invalid character due to the is_base64() check in its
// while loop condition, making this edge case harmless in practice. // while loop condition, making this edge case harmless in practice.
static inline uint8_t base64_find_char(char c) { static inline uint8_t base64_find_char(char c) {
const char *pos = strchr(BASE64_CHARS, c); const void *ptr = memchr(BASE64_CHARS, c, sizeof(BASE64_CHARS));
return pos ? (pos - BASE64_CHARS) : 0; return ptr ? (static_cast<const char *>(ptr) - BASE64_CHARS) : 0;
} }
static inline bool is_base64(char c) { return (isalnum(c) || (c == '+') || (c == '/')); } static inline bool is_base64(char c) { return (isalnum(c) || (c == '+') || (c == '/')); }