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Fix custom vsnprint formatting for width, leading zeros, and %X #34

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Merged
emrainey merged 1 commit into from
Jun 27, 2026
Merged

Fix custom vsnprint formatting for width, leading zeros, and %X #34

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2 changes: 1 addition & 1 deletion applications/nucleo-demo/source/Demo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@ void Demo::OnEntry(DemoState state) {
}

DemoState Demo::OnCycle(DemoState state) {
jarnax::print("Demo::OnCycle: %u\r\n", static_cast<std::uint8_t>(state));
// jarnax::print("Demo::OnCycle: %u\r\n", static_cast<std::uint8_t>(state));
if (state == DemoState::StartUp) {
state = DemoState::KeyLoop;
} else if (state == DemoState::KeyLoop) {
Expand Down
215 changes: 117 additions & 98 deletions modules/core/source/vsnprint.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -38,7 +38,7 @@ static U clamp_to_range(T value, U min, U max) {
/// @param base The base to parse the number in
/// @return The index at the exclusive end of the number
template <typename T>
static unsigned long print_number(unsigned long start, char buffer[], T num, unsigned int base) {
static unsigned long print_number(unsigned long start, char buffer[], T num, unsigned int base, unsigned int width = 0, bool leading_zero = false, bool uppercase = false, bool is_negative = false) {
// the digits cover base 2, base 8 (don't use) base 10, base 12, base 16 and base 64
static constexpr char const *const digits =
"0123456789abcdef"
Expand All @@ -49,72 +49,72 @@ static unsigned long print_number(unsigned long start, char buffer[], T num, uns
unsigned long offset = 0;
char backwards_digits[digit_places_limit]; // hold the value temporarily

if (base == base2) {
if (num < 0b10) {
buffer[start] = digits[num];
return start + 1;
} else {
if (num == 0) {
backwards_digits[offset++] = '0';
} else {
if (base == base2) {
while (num != 0) {
backwards_digits[offset] = digits[num & 1];
offset++;
backwards_digits[offset++] = digits[num & 1];
num >>= 1;
}
}
}
if (base == base8) {
if (num < 8) {
buffer[start] = digits[num];
return start + 1;
} else {
} else if (base == base8) {
while (num != 0) {
backwards_digits[offset] = digits[num & 7];
offset++;
backwards_digits[offset++] = digits[num & 7];
num >>= 3;
}
}
}
if (base == base10) {
if (num < 10) {
buffer[start] = digits[num];
return start + 1;
} else {
} else if (base == base10) {
while (num != 0) {
backwards_digits[offset] = digits[num % 10];
offset++;
backwards_digits[offset++] = digits[num % 10];
num /= 10;
}
}
}
if (base == base16) {
if (num < 0x10) {
buffer[start] = digits[num];
return start + 1;
} else {
} else if (base == base16) {
while (num != 0) {
backwards_digits[offset] = digits[num & 0xF];
offset++;
char d = digits[num & 0xF];
if (uppercase && d >= 'a' && d <= 'z') {
d = d - 'a' + 'A';
}
backwards_digits[offset++] = d;
num >>= 4;
}
}
}
if (base == base64) {
if (num < 0x40) {
buffer[start] = digits[num];
return start + 1;
} else {
} else if (base == base64) {
while (num != 0) {
backwards_digits[offset] = digits[num & 0x3F];
offset++;
backwards_digits[offset++] = digits[num & 0x3F];
num >>= 6;
}
}
}
if (offset > 0) {
for (unsigned int i = 0; i < offset; i++) {
buffer[start + i] = backwards_digits[offset - i - 1];

// Determine how many characters we will print before padding
unsigned int total_chars = static_cast<unsigned int>(offset) + (is_negative ? 1U : 0U);
unsigned long current = start;

// Space padding (leading_zero = false) goes before the sign
if (!leading_zero && width > total_chars) {
unsigned int padding = width - total_chars;
for (unsigned int i = 0; i < padding; i++) {
buffer[current++] = ' ';
}
}

// Print the sign if negative
if (is_negative) {
buffer[current++] = '-';
}

// Zero padding (leading_zero = true) goes after the sign
if (leading_zero && width > total_chars) {
unsigned int padding = width - total_chars;
for (unsigned int i = 0; i < padding; i++) {
buffer[current++] = '0';
}
}
return start + offset;

// Print the digits in correct order (reverse of backwards_digits)
for (unsigned int i = 0; i < offset; i++) {
buffer[current++] = backwards_digits[offset - i - 1];
}

return current;
}

/// @brief Parses the number and prints it in the specified base in the buffer
Expand All @@ -125,12 +125,13 @@ static unsigned long print_number(unsigned long start, char buffer[], T num, uns
/// @param base The base to parse the number in
/// @return The index at the exclusive end of the number
template <typename T>
static unsigned long print_signed_number(unsigned long start, char buffer[], T num, unsigned int base) {
static unsigned long print_signed_number(unsigned long start, char buffer[], T num, unsigned int base, unsigned int width = 0, bool leading_zero = false) {
if (num < 0) {
buffer[start] = '-';
return print_number(start + 1, buffer, -num, base);
// Safe absolute value conversion using uint64_t to avoid signed integer overflow on INT_MIN
uint64_t abs_val = static_cast<uint64_t>(-static_cast<int64_t>(num));
return print_number(start, buffer, abs_val, base, width, leading_zero, false, true);
} else {
return print_number(start, buffer, num, base);
return print_number(start, buffer, static_cast<uint64_t>(num), base, width, leading_zero, false, false);
}
}

Expand All @@ -145,6 +146,25 @@ unsigned long vsnprint(char buffer[], size_t buffer_size, const char *format, va
if (*format == '%') {
format++;

// Handle leading zero modifier
bool leading_zero = false;
if (*format == '0') {
leading_zero = true;
format++;
}

// Handle width modifier
unsigned int width = 0;
if (is_digit(*format)) {
while (is_digit(*format)) {
width = width * 10U + static_cast<unsigned int>(*format - '0');
format++;
}
if (width > digit_places_limit) {
width = digit_places_limit;
}
}

// Handle %l modifiers
bool longlong_modifier = false;
bool long_modifier = false;
Expand Down Expand Up @@ -177,27 +197,6 @@ unsigned long vsnprint(char buffer[], size_t buffer_size, const char *format, va
format++;
}

// Handle leading zero modifier
// bool leading_zero = false;
// if (*format == '0') {
// leading_zero = true;
// format++;
// }
// bool specific_digits = false;
// if (is_digit(*format)) {
// specific_digits = true;
// unsigned int digits = 0;
// while (is_digit(*format)) {
// digits = digits * 10 + (*format - '0');
// format++;
// }
// if (digits > digit_places_limit) {
// digits = digit_places_limit;
// }
// }
// (void)leading_zero; // @TODO unused
// (void)specific_digits; // @TODO unused

switch (*format) {
case 's': {
const char *str = va_arg(args, const char *);
Expand All @@ -212,78 +211,99 @@ unsigned long vsnprint(char buffer[], size_t buffer_size, const char *format, va
if (longlong_modifier) {
int64_t num = va_arg(args, int64_t);
num = clamp_to_range(num, std::numeric_limits<int64_t>::min(), std::numeric_limits<int64_t>::max());
index = print_signed_number(index, buffer, num, base10);
index = print_signed_number(index, buffer, num, base10, width, leading_zero);
} else if (long_modifier) {
int32_t num = va_arg(args, int32_t);
num = clamp_to_range(num, std::numeric_limits<int32_t>::min(), std::numeric_limits<int32_t>::max());
index = print_signed_number(index, buffer, num, base10);
index = print_signed_number(index, buffer, num, base10, width, leading_zero);
} else if (half_modifier) {
int value = static_cast<int16_t>(va_arg(args, int));
int16_t num = clamp_to_range(value, std::numeric_limits<int16_t>::min(), std::numeric_limits<int16_t>::max());
index = print_signed_number(index, buffer, num, base10);
index = print_signed_number(index, buffer, num, base10, width, leading_zero);
} else if (halfhalf_modifier) {
int value = va_arg(args, int);
int8_t num = clamp_to_range(value, std::numeric_limits<int8_t>::min(), std::numeric_limits<int8_t>::max());
index = print_signed_number(index, buffer, num, base10);
// } else if (size_modifier) {
// ssize_t value = va_arg(args, ssize_t);
// num = clamp_to_range(value, std::numeric_limits<ssize_t>::min(), std::numeric_limits<ssize_t>::max());
// index = print_signed_number(index, buffer, num, base10);
index = print_signed_number(index, buffer, num, base10, width, leading_zero);
} else {
auto num = va_arg(args, int);
index = print_signed_number(index, buffer, num, base10);
index = print_signed_number(index, buffer, num, base10, width, leading_zero);
}
break;
}
case 'u': {
if (longlong_modifier) {
uint64_t num = va_arg(args, uint64_t);
num = clamp_to_range(num, std::numeric_limits<uint64_t>::min(), std::numeric_limits<uint64_t>::max());
index = print_number(index, buffer, num, base10);
index = print_number(index, buffer, num, base10, width, leading_zero);
} else if (long_modifier) {
uint32_t num = va_arg(args, uint32_t);
num = clamp_to_range(num, std::numeric_limits<uint32_t>::min(), std::numeric_limits<uint32_t>::max());
index = print_number(index, buffer, num, base10);
index = print_number(index, buffer, num, base10, width, leading_zero);
} else if (half_modifier) {
unsigned int value = va_arg(args, unsigned int);
uint16_t num = clamp_to_range(value, std::numeric_limits<uint16_t>::min(), std::numeric_limits<uint16_t>::max());
index = print_number(index, buffer, num, base10);
index = print_number(index, buffer, num, base10, width, leading_zero);
} else if (halfhalf_modifier) {
unsigned int value = va_arg(args, unsigned int);
uint8_t num = clamp_to_range(value, std::numeric_limits<uint8_t>::min(), std::numeric_limits<uint8_t>::max());
index = print_number(index, buffer, num, base10);
index = print_number(index, buffer, num, base10, width, leading_zero);
} else if (size_modifier) {
size_t num = va_arg(args, size_t);
index = print_number(index, buffer, num, base10);
index = print_number(index, buffer, num, base10, width, leading_zero);
} else {
unsigned int num = va_arg(args, unsigned int);
index = print_number(index, buffer, num, base10);
index = print_number(index, buffer, num, base10, width, leading_zero);
}
break;
}
case 'x': {
buffer[index++] = '0';
buffer[index++] = 'x';
unsigned int sub_width = (width > 2) ? (width - 2) : 0;
if (longlong_modifier) {
uint64_t num = va_arg(args, uint64_t);
index = print_number(index, buffer, num, base16);
index = print_number(index, buffer, num, base16, sub_width, leading_zero, false);
} else if (long_modifier) {
uint32_t num = va_arg(args, uint32_t); // 32 bits
index = print_number(index, buffer, num, base16);
uint32_t num = va_arg(args, uint32_t);
index = print_number(index, buffer, num, base16, sub_width, leading_zero, false);
} else if (half_modifier) {
unsigned int value = va_arg(args, unsigned int);
uint16_t num = clamp_to_range(value, std::numeric_limits<uint16_t>::min(), std::numeric_limits<uint16_t>::max());
index = print_number(index, buffer, num, base16);
index = print_number(index, buffer, num, base16, sub_width, leading_zero, false);
} else if (halfhalf_modifier) {
unsigned int value = va_arg(args, unsigned int);
uint8_t num = clamp_to_range(value, std::numeric_limits<uint8_t>::min(), std::numeric_limits<uint8_t>::max());
index = print_number(index, buffer, num, base16);
index = print_number(index, buffer, num, base16, sub_width, leading_zero, false);
} else if (size_modifier) {
size_t num = va_arg(args, size_t);
index = print_number(index, buffer, num, base16);
index = print_number(index, buffer, num, base16, sub_width, leading_zero, false);
} else {
uint32_t num = va_arg(args, unsigned int);
index = print_number(index, buffer, num, base16);
index = print_number(index, buffer, num, base16, sub_width, leading_zero, false);
}
break;
}
case 'X': {
if (longlong_modifier) {
uint64_t num = va_arg(args, uint64_t);
index = print_number(index, buffer, num, base16, width, leading_zero, true);
} else if (long_modifier) {
uint32_t num = va_arg(args, uint32_t);
index = print_number(index, buffer, num, base16, width, leading_zero, true);
} else if (half_modifier) {
unsigned int value = va_arg(args, unsigned int);
uint16_t num = clamp_to_range(value, std::numeric_limits<uint16_t>::min(), std::numeric_limits<uint16_t>::max());
index = print_number(index, buffer, num, base16, width, leading_zero, true);
} else if (halfhalf_modifier) {
unsigned int value = va_arg(args, unsigned int);
uint8_t num = clamp_to_range(value, std::numeric_limits<uint8_t>::min(), std::numeric_limits<uint8_t>::max());
index = print_number(index, buffer, num, base16, width, leading_zero, true);
} else if (size_modifier) {
size_t num = va_arg(args, size_t);
index = print_number(index, buffer, num, base16, width, leading_zero, true);
} else {
uint32_t num = va_arg(args, unsigned int);
index = print_number(index, buffer, num, base16, width, leading_zero, true);
}
break;
}
Expand Down Expand Up @@ -321,7 +341,8 @@ unsigned long vsnprint(char buffer[], size_t buffer_size, const char *format, va
}
buffer[index++] = '0';
buffer[index++] = 'b';
index = print_number(index, buffer, num, base2);
unsigned int sub_width = (width > 2) ? (width - 2) : 0;
index = print_number(index, buffer, num, base2, sub_width, leading_zero, false);
break;
}
default:
Expand All @@ -336,8 +357,6 @@ unsigned long vsnprint(char buffer[], size_t buffer_size, const char *format, va
format++;
}

// FIXME determine if we've run over.

// null terminate the string
if (index >= buffer_size) {
index = buffer_size - 1;
Expand Down
1 change: 1 addition & 0 deletions modules/core/tests/CMakeLists.txt
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Expand Up @@ -23,6 +23,7 @@ host_unit_test(NAME core
${CMAKE_CURRENT_SOURCE_DIR}/catch2-tokenizer.cpp
# ${CMAKE_CURRENT_SOURCE_DIR}/catch2-units.cpp # requires information from the Configuration and Architecture
${CMAKE_CURRENT_SOURCE_DIR}/catch2-variants.cpp
${CMAKE_CURRENT_SOURCE_DIR}/catch2-vsnprint.cpp
${CMAKE_CURRENT_SOURCE_DIR}/source/conversions.cpp
${_GENERATED_CORE_TESTS}
LIBRARIES
Expand Down
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