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Code Issues Releases Wiki Activity

[helpers] Add base85 support (#13254)

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Co-authored-by: J. Nick Koston <nick@koston.org>
This commit is contained in:
Keith Burzinski
2026-01-15 20:22:05 -06:00
committed by GitHub
parent 535c3eb2a2
commit 2eabc1b96b
2 changed files with 57 additions and 0 deletions
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49
esphome/core/helpers.cpp
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@@ -617,6 +617,55 @@ std::vector<uint8_t> base64_decode(const std::string &encoded_string) {
return ret;
}
/// Encode int32 to 5 base85 characters + null terminator
/// Standard ASCII85 alphabet: '!' (33) = 0 through 'u' (117) = 84
inline void base85_encode_int32(int32_t value, std::span<char, BASE85_INT32_ENCODED_SIZE> output) {
uint32_t v = static_cast<uint32_t>(value);
// Encode least significant digit first, then reverse
for (int i = 4; i >= 0; i--) {
output[i] = static_cast<char>('!' + (v % 85));
v /= 85;
}
output[5] = '\0';
}
/// Decode 5 base85 characters to int32
inline bool base85_decode_int32(const char *input, int32_t &out) {
uint8_t c0 = static_cast<uint8_t>(input[0] - '!');
uint8_t c1 = static_cast<uint8_t>(input[1] - '!');
uint8_t c2 = static_cast<uint8_t>(input[2] - '!');
uint8_t c3 = static_cast<uint8_t>(input[3] - '!');
uint8_t c4 = static_cast<uint8_t>(input[4] - '!');
// Each digit must be 0-84. Since uint8_t wraps, chars below '!' become > 84
if (c0 > 84 || c1 > 84 || c2 > 84 || c3 > 84 || c4 > 84)
return false;
// 85^4 = 52200625, 85^3 = 614125, 85^2 = 7225, 85^1 = 85
out = static_cast<int32_t>(c0 * 52200625u + c1 * 614125u + c2 * 7225u + c3 * 85u + c4);
return true;
}
/// Decode base85 string directly into vector (no intermediate buffer)
bool base85_decode_int32_vector(const std::string &base85, std::vector<int32_t> &out) {
size_t len = base85.size();
if (len % 5 != 0)
return false;
out.clear();
const char *ptr = base85.data();
const char *end = ptr + len;
while (ptr < end) {
int32_t value;
if (!base85_decode_int32(ptr, value))
return false;
out.push_back(value);
ptr += 5;
}
return true;
}
// Colors
float gamma_correct(float value, float gamma) {

8
esphome/core/helpers.h
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@@ -1086,6 +1086,14 @@ std::vector<uint8_t> base64_decode(const std::string &encoded_string);
size_t base64_decode(std::string const &encoded_string, uint8_t *buf, size_t buf_len);
size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *buf, size_t buf_len);
/// Size of buffer needed for base85 encoded int32 (5 chars + null terminator)
static constexpr size_t BASE85_INT32_ENCODED_SIZE = 6;
void base85_encode_int32(int32_t value, std::span<char, BASE85_INT32_ENCODED_SIZE> output);
bool base85_decode_int32(const char *input, int32_t &out);
bool base85_decode_int32_vector(const std::string &base85, std::vector<int32_t> &out);
///@}
/// @name Colors