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Split uint32_to_str/frac_to_str into internal and public API

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- uint32_to_str_(): raw pointer, internal use
- uint32_to_str(): template with compile-time buffer size check
- frac_to_str_(): raw pointer, internal use
- small_pow10(): simplify to ternary chain
This commit is contained in:
J. Nick Koston
2026-04-08 21:01:32 -10:00
parent e52c3b01e6
commit 3b45179948
3 changed files with 48 additions and 33 deletions
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esphome/core/helpers.cpp
+2 -2
View File
@@ -539,10 +539,10 @@ static size_t value_accuracy_to_buf_fast(char *buf, float value, int8_t accuracy
// float*int loses bits at exact-half boundaries (e.g. 23.45f*10 = 234.5 in float,
// but snprintf sees 234.500007... via double promotion and rounds differently).
uint32_t scaled = static_cast<uint32_t>(lrint(static_cast<double>(value) * mult));
p = uint32_to_str(p, scaled / mult);
p = uint32_to_str_(p, scaled / mult);
if (accuracy_decimals > 0) {
*p++ = '.';
p = frac_to_str(p, scaled % mult, mult / 10);
p = frac_to_str_(p, scaled % mult, mult / 10);
}
*p = '\0';
return static_cast<size_t>(p - buf);
esphome/core/helpers.h
+18 -15
View File
@@ -1311,20 +1311,14 @@ inline char *buf_append_sep_str(char *buf, size_t remaining, char separator, con
}
/// Return 10^n for small non-negative n (0-3) as uint32_t, avoiding float.
inline uint32_t small_pow10(int8_t n) {
if (n == 1) {
return 10;
} else if (n == 2) {
return 100;
} else if (n == 3) {
return 1000;
}
return 1;
}
inline uint32_t small_pow10(int8_t n) { return n == 3 ? 1000 : n == 2 ? 100 : n == 1 ? 10 : 1; }
/// Write unsigned 32-bit integer to buffer. Returns pointer past last char written.
/// Buffer must have at least 10 bytes free (max uint32 is 4294967295).
inline char *uint32_to_str(char *buf, uint32_t val) {
/// Minimum buffer size for uint32_to_str: 10 digits + null terminator.
static constexpr size_t UINT32_MAX_STR_SIZE = 11;
/// Write unsigned 32-bit integer to buffer (internal, no size check).
/// Buffer must have at least 10 bytes free. Returns pointer past last char written.
inline char *uint32_to_str_(char *buf, uint32_t val) {
if (val == 0) {
*buf++ = '0';
return buf;
@@ -1338,10 +1332,19 @@ inline char *uint32_to_str(char *buf, uint32_t val) {
return buf;
}
/// Write fractional digits with leading zeros to buffer.
/// Write unsigned 32-bit integer to buffer with compile-time size check.
/// Null-terminates the output. Returns number of chars written (excluding null).
template<size_t N> inline size_t uint32_to_str(char (&buf)[N], uint32_t val) {
static_assert(N >= UINT32_MAX_STR_SIZE, "Buffer too small for uint32 (need 11 bytes)");
char *end = uint32_to_str_(buf, val);
*end = '\0';
return static_cast<size_t>(end - buf);
}
/// Write fractional digits with leading zeros to buffer (internal, no size check).
/// frac is the fractional value, divisor is the highest place value (e.g. 100 for 3 digits).
/// Returns pointer past last char written.
inline char *frac_to_str(char *buf, uint32_t frac, uint32_t divisor) {
inline char *frac_to_str_(char *buf, uint32_t frac, uint32_t divisor) {
while (divisor > 0) {
*buf++ = '0' + static_cast<char>(frac / divisor);
frac %= divisor;
tests/components/core/test_helpers.cpp
+28 -16
View File
@@ -16,7 +16,7 @@ TEST(SmallPow10, Three) { EXPECT_EQ(small_pow10(3), 1000u); }
TEST(Uint32ToStr, Zero) {
char buf[12];
char *end = uint32_to_str(buf, 0);
char *end = uint32_to_str_(buf, 0);
*end = '\0';
EXPECT_STREQ(buf, "0");
EXPECT_EQ(end - buf, 1);
@@ -24,14 +24,14 @@ TEST(Uint32ToStr, Zero) {
TEST(Uint32ToStr, SingleDigit) {
char buf[12];
char *end = uint32_to_str(buf, 7);
char *end = uint32_to_str_(buf, 7);
*end = '\0';
EXPECT_STREQ(buf, "7");
}
TEST(Uint32ToStr, MultiDigit) {
char buf[12];
char *end = uint32_to_str(buf, 12345);
char *end = uint32_to_str_(buf, 12345);
*end = '\0';
EXPECT_STREQ(buf, "12345");
EXPECT_EQ(end - buf, 5);
@@ -39,7 +39,7 @@ TEST(Uint32ToStr, MultiDigit) {
TEST(Uint32ToStr, Large) {
char buf[12];
char *end = uint32_to_str(buf, 4294967295u);
char *end = uint32_to_str_(buf, 4294967295u);
*end = '\0';
EXPECT_STREQ(buf, "4294967295");
EXPECT_EQ(end - buf, 10);
@@ -49,24 +49,36 @@ TEST(Uint32ToStr, PowersOfTen) {
char buf[12];
char *end;
end = uint32_to_str(buf, 10);
end = uint32_to_str_(buf, 10);
*end = '\0';
EXPECT_STREQ(buf, "10");
end = uint32_to_str(buf, 100);
end = uint32_to_str_(buf, 100);
*end = '\0';
EXPECT_STREQ(buf, "100");
end = uint32_to_str(buf, 1000);
end = uint32_to_str_(buf, 1000);
*end = '\0';
EXPECT_STREQ(buf, "1000");
}
// --- frac_to_str() ---
// --- uint32_to_str() (public, template with size check) ---
TEST(Uint32ToStr, PublicApi) {
char buf[UINT32_MAX_STR_SIZE];
EXPECT_EQ(uint32_to_str(buf, 0), 1u);
EXPECT_STREQ(buf, "0");
EXPECT_EQ(uint32_to_str(buf, 12345), 5u);
EXPECT_STREQ(buf, "12345");
EXPECT_EQ(uint32_to_str(buf, 4294967295u), 10u);
EXPECT_STREQ(buf, "4294967295");
}
// --- frac_to_str_() ---
TEST(FracToStr, OneDigit) {
char buf[8];
char *end = frac_to_str(buf, 5, 1);
char *end = frac_to_str_(buf, 5, 1);
*end = '\0';
EXPECT_STREQ(buf, "5");
EXPECT_EQ(end - buf, 1);
@@ -74,14 +86,14 @@ TEST(FracToStr, OneDigit) {
TEST(FracToStr, TwoDigits) {
char buf[8];
char *end = frac_to_str(buf, 46, 10);
char *end = frac_to_str_(buf, 46, 10);
*end = '\0';
EXPECT_STREQ(buf, "46");
}
TEST(FracToStr, ThreeDigits) {
char buf[8];
char *end = frac_to_str(buf, 456, 100);
char *end = frac_to_str_(buf, 456, 100);
*end = '\0';
EXPECT_STREQ(buf, "456");
EXPECT_EQ(end - buf, 3);
@@ -89,22 +101,22 @@ TEST(FracToStr, ThreeDigits) {
TEST(FracToStr, LeadingZeros) {
char buf[8];
char *end = frac_to_str(buf, 1, 100);
char *end = frac_to_str_(buf, 1, 100);
*end = '\0';
EXPECT_STREQ(buf, "001");
end = frac_to_str(buf, 5, 10);
end = frac_to_str_(buf, 5, 10);
*end = '\0';
EXPECT_STREQ(buf, "05");
}
TEST(FracToStr, AllZeros) {
char buf[8];
char *end = frac_to_str(buf, 0, 100);
char *end = frac_to_str_(buf, 0, 100);
*end = '\0';
EXPECT_STREQ(buf, "000");
end = frac_to_str(buf, 0, 1);
end = frac_to_str_(buf, 0, 1);
*end = '\0';
EXPECT_STREQ(buf, "0");
}
@@ -112,7 +124,7 @@ TEST(FracToStr, AllZeros) {
TEST(FracToStr, ZeroDivisor) {
char buf[8];
buf[0] = 'X';
char *end = frac_to_str(buf, 0, 0);
char *end = frac_to_str_(buf, 0, 0);
EXPECT_EQ(end, buf); // writes nothing
}