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Merge pull request #30 from Sympatron/master
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Add support for padding in snprintf
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@thejpster
thejpster authored Oct 28, 2024
2 parents 150a689 + ceba619 commit 4f6da13
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Showing 3 changed files with 379 additions and 231 deletions.
2 changes: 1 addition & 1 deletion .github/workflows/build.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ jobs:
- uses: actions-rs/toolchain@v1
with:
profile: minimal
toolchain: 1.75.0 # clippy is too much of a moving target at the moment
toolchain: 1.77.0 # clippy is too much of a moving target at the moment
override: true
components: clippy
- uses: actions-rs/clippy-check@v1
Expand Down
271 changes: 139 additions & 132 deletions src/snprintf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,9 @@
static void write_output(
char out, char* restrict str, size_t max, size_t* written );

static void write_padding(
char* restrict str, size_t size, size_t* written, size_t len, unsigned long width, unsigned long precision, bool zero_pad, bool is_negative );

static char upcase(char c);

/* ======================================================================== *
Expand Down Expand Up @@ -84,7 +87,7 @@ extern unsigned long int strtoul(const char* str, char** endptr, int base);
* - c (char)
* - s (null-terminated string)
* - % (literal percent sign)
* - qualifiers: l, ll, z
* - qualifiers: l, ll, z, width, (non-string) precision, left-space-pad, zero-pad
*
* Does not support:
*
Expand All @@ -96,7 +99,7 @@ extern unsigned long int strtoul(const char* str, char** endptr, int base);
* - f (decimal floating point)
* - g (the shorter of %e and %f)
* - G (the shorter of %E and %f)
* - qualifiers: L, width, (non-string) precision, -, +, space-pad, zero-pad, etc
* - qualifiers: L, -, +, right-pad, etc
*
* @param str the output buffer to write to
* @param size the size of the output buffer
Expand All @@ -113,6 +116,8 @@ int vsnprintf(
int is_long = 0;
bool is_size_t = false;
unsigned long precision = -1;
unsigned long width = 0;
bool zero_pad = false;

while ( *fmt )
{
Expand All @@ -138,173 +143,93 @@ int vsnprintf(
is_escape = true;
break;
case 'u':
if ( is_size_t )
{
// Render %zu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
size_t su = va_arg( ap, size_t );
utoa( su, s, sizeof(s), 10 );
for ( const char* p = s; *p != '\0'; p++ )
unsigned long long ll = 0;
if ( is_size_t )
{
write_output( *p, str, size, &written );
// Render %zu
ll = va_arg( ap, size_t );
}
}
else if ( is_long == 2 )
{
// Render %lu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
unsigned long long ll = va_arg( ap, unsigned long long );
utoa( ll, s, sizeof(s), 10 );
for ( const char* p = s; *p != '\0'; p++ )
else if ( is_long == 2 )
{
write_output( *p, str, size, &written );
// Render %llu
ll = va_arg( ap, unsigned long long );
}
}
else if ( is_long == 1 )
{
// Render %lu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
unsigned long l = va_arg( ap, unsigned long );
utoa( l, s, sizeof(s), 10 );
for ( const char* p = s; *p != '\0'; p++ )
else if ( is_long == 1 )
{
write_output( *p, str, size, &written );
// Render %lu
ll = va_arg( ap, unsigned long );
}
}
else
{
// Render %u
unsigned int i = va_arg( ap, unsigned int );
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
utoa( i, s, sizeof(s), 10 );
for ( const char* p = s; *p != '\0'; p++ )
else
{
write_output( *p, str, size, &written );
// Render %u
ll = va_arg( ap, unsigned int );
}
}
break;
case 'x':
if ( is_size_t )
{
// Render %zu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
size_t su = va_arg( ap, size_t );
utoa( su, s, sizeof(s), 16 );
utoa( ll, s, sizeof(s), 10 );
write_padding( str, size, &written, strlen(s), width, precision, zero_pad, false );
for ( const char* p = s; *p != '\0'; p++ )
{
write_output( *p, str, size, &written );
}
}
else if ( is_long == 2 )
break;
case 'x':
case 'X':
// Render %x and %X
{
// Render %llu
unsigned long long ll;
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
unsigned long long ll = va_arg( ap, unsigned long long );
utoa( ll, s, sizeof(s), 16 );
for ( const char* p = s; *p != '\0'; p++ )
if ( is_size_t )
{
write_output( *p, str, size, &written );
ll = va_arg( ap, size_t );
}
}
else if ( is_long == 1 )
{
// Render %lu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
unsigned long l = va_arg( ap, unsigned long );
utoa( l, s, sizeof(s), 16 );
for ( const char* p = s; *p != '\0'; p++ )
else if ( is_long == 2 )
{
write_output( *p, str, size, &written );
ll = va_arg( ap, unsigned long long );
}
}
else
{
// Render %u
unsigned int i = va_arg( ap, unsigned int );
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
utoa( i, s, sizeof(s), 16 );
for ( const char* p = s; *p != '\0'; p++ )
else if ( is_long == 1 )
{
write_output( *p, str, size, &written );
ll = va_arg( ap, unsigned long );
}
}
break;
case 'X':
if ( is_size_t )
{
// Render %zu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
size_t su = va_arg( ap, size_t );
utoa( su, s, sizeof(s), 16 );
for ( const char* p = s; *p != '\0'; p++ )
else
{
write_output( upcase(*p), str, size, &written );
ll = va_arg( ap, unsigned int );
}
}
else if ( is_long == 2 )
{
// Render %llu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
unsigned long long ll = va_arg( ap, unsigned long long );
utoa( ll, s, sizeof(s), 16 );
for ( const char* p = s; *p != '\0'; p++ )
write_padding( str, size, &written, strlen(s), width, precision, zero_pad, false );
for (const char* p = s; *p != '\0'; p++)
{
write_output( upcase(*p), str, size, &written );
}
}
else if ( is_long == 1 )
{
// Render %lu
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
unsigned long l = va_arg( ap, unsigned long );
utoa( l, s, sizeof(s), 16 );
for ( const char* p = s; *p != '\0'; p++ )
{
write_output( upcase(*p), str, size, &written );
}
}
else
{
// Render %u
unsigned int i = va_arg( ap, unsigned int );
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
utoa( i, s, sizeof(s), 16 );
for ( const char* p = s; *p != '\0'; p++ )
{
write_output( upcase(*p), str, size, &written );
char output_char = (*fmt == 'X') ? upcase(*p) : *p;
write_output( output_char, str, size, &written );
}
}
break;
case 'i':
case 'd':
if ( is_long == 2 )
{
// Render %ld
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
signed long long ll = va_arg( ap, signed long long );
itoa( ll, s, sizeof(s), 10 );
for ( const char* p = s; *p != '\0'; p++ )
signed long long ll = 0;
unsigned long long ull = 0;
if ( is_long == 2 )
{
write_output( *p, str, size, &written );
// Render %lld
ll = va_arg( ap, signed long long );
}
}
else if ( is_long == 1 )
{
// Render %ld
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
signed long l = va_arg( ap, signed long );
itoa( l, s, sizeof(s), 10 );
for ( const char* p = s; *p != '\0'; p++ )
else if ( is_long == 1 )
{
write_output( *p, str, size, &written );
// Render %ld
ll = va_arg( ap, signed long );
}
}
else
{
// Render %d
signed int i = va_arg( ap, signed int );
char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
itoa( i, s, sizeof(s), 10 );
else
{
// Render %d
ll = va_arg( ap, signed int );
}
bool is_negative = ll < 0;
ull = is_negative ? -ll : ll;
utoa( ull, s, sizeof(s), 10 );
write_padding( str, size, &written, strlen(s), width, precision, zero_pad, is_negative );
for ( const char* p = s; *p != '\0'; p++ )
{
write_output( *p, str, size, &written );
Expand All @@ -323,6 +248,12 @@ int vsnprintf(
{
const char *s = va_arg( ap, const char* );
unsigned long count = precision;

size_t len = strlen(s);
if (precision != (unsigned long)-1 && precision < len) {
len = precision;
}
write_padding( str, size, &written, len, width, precision, false, false );

while (count > 0 && *s != '\0')
{
Expand All @@ -336,7 +267,7 @@ int vsnprintf(
}
break;
case '.':
// Render a precision specifier
// Parse a precision specifier
{
// Next up is either a number or a '*' that signifies that the number is in the arguments list
char next = *++fmt;
Expand All @@ -356,6 +287,27 @@ int vsnprintf(
is_escape = true;
}
break;
case '0':
// Parse zero padding specifier
zero_pad = true;
fmt++;
/* fall through */
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
// Parse padding specifier
width = strtoul(fmt, (char**) &fmt, 10);
// Strtoul sets the fmt pointer to the char after the number,
// however the code expects the char before that.
fmt--;
is_escape = true;
break;
case '%':
write_output( '%', str, size, &written );
break;
Expand All @@ -378,6 +330,9 @@ int vsnprintf(
is_escape = true;
is_long = 0;
is_size_t = false;
zero_pad = false;
width = 0;
precision = -1;
break;
default:
write_output( *fmt, str, size, &written );
Expand Down Expand Up @@ -451,6 +406,58 @@ static void write_output(
}
}

/**
* write_padding - Write padding to the output buffer.
*
* @param str the buffer to write to
* @param size the total size of `str`
* @param written pass in the number of characters in the buffer; is increased
* by one regardless of whether we wrote to the buffer
* @param len the length of the string to write
* @param width the total width of the padding
* @param precision the precision of the padding
* @param zero_pad whether to zero pad the string
* @param is_negative whether the number is negative
*/
static void write_padding(char* restrict str, size_t size, size_t* written, size_t len, unsigned long width, unsigned long precision, bool zero_pad, bool is_negative) {
if ( is_negative )
{
len++;
}
unsigned long pad_len = width > len ? width - len : 0;
unsigned long zero_pad_len = 0;
if ( precision != 0 && precision != (unsigned long)-1 )
{
if ( is_negative )
{
zero_pad_len = precision >= len ? precision - len + 1 : 0;
}
else
{
zero_pad_len = precision >= len ? precision - len : 0;
}
}
else if ( zero_pad && precision == (unsigned long)-1 )
{
zero_pad_len = pad_len;
}
// Apply whitespace padding if needed
pad_len = (zero_pad_len > pad_len) ? 0 : pad_len - zero_pad_len;
for (unsigned long i = 0; i < pad_len; i++)
{
write_output( ' ', str, size, written );
}
// Apply zero padding if needed
if (is_negative)
{
write_output( '-', str, size, written );
}
for (unsigned long i = 0; i < zero_pad_len; i++)
{
write_output( '0', str, size, written );
}
}

/**
* Converts 'a'..'z' to 'A'..'Z', leaving all other characters unchanged.
*/
Expand Down
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