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prf.c: remove buffer limitation on field width and padding for integers
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Zero-padding of integers took place in the on-stack buffer before
justification. Let's perform that padding on the fly while sending
out data instead.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
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@nashif
Nicolas Pitre authored and nashif committed Jul 15, 2019
1 parent 33312cf commit 7c7f107
Showing 1 changed file with 73 additions and 84 deletions.
157 changes: 73 additions & 84 deletions lib/libc/minimal/source/stdout/prf.c
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Expand Up @@ -46,48 +46,36 @@ static void _uc(char *buf)
} while (*buf++);
}

/*
* Convention note: "end" as passed in is the standard "byte after
* last character" style, but...
*/
static int _reverse_and_pad(char *start, char *end, int minlen)
{
int len;

while (end - start < minlen) {
*end++ = '0';
}

*end = 0;
len = end - start;
for (end--; end > start; end--, start++) {
char tmp = *end;
*end = *start;
*start = tmp;
}
return len;
}

/*
* Writes the specified number into the buffer in the given base,
* using the digit characters 0-9a-z (i.e. base>36 will start writing
* odd bytes), padding with leading zeros up to the minimum length.
* odd bytes).
*/
static int _to_x(char *buf, unsigned VALTYPE n, unsigned int base, int minlen)
static int _to_x(char *buf, unsigned VALTYPE n, unsigned int base)
{
char *buf0 = buf;
char *start = buf;
int len;

do {
unsigned int d = n % base;

n /= base;
*buf++ = '0' + d + (d > 9 ? ('a' - '0' - 10) : 0);
} while (n);
return _reverse_and_pad(buf0, buf, minlen);

*buf = 0;
len = buf - start;

for (buf--; buf > start; buf--, start++) {
char tmp = *buf;
*buf = *start;
*start = tmp;
}

return len;
}

static int _to_hex(char *buf, unsigned VALTYPE value,
bool alt_form, int precision, char prefix)
static int _to_hex(char *buf, unsigned VALTYPE value, bool alt_form, char prefix)
{
int len;
char *buf0 = buf;
Expand All @@ -97,16 +85,15 @@ static int _to_hex(char *buf, unsigned VALTYPE value,
*buf++ = 'x';
}

len = _to_x(buf, value, 16, precision);
len = _to_x(buf, value, 16);
if (prefix == 'X') {
_uc(buf0);
}

return len + (buf - buf0);
}

static int _to_octal(char *buf, unsigned VALTYPE value,
bool alt_form, int precision)
static int _to_octal(char *buf, unsigned VALTYPE value, bool alt_form)
{
char *buf0 = buf;

Expand All @@ -118,16 +105,15 @@ static int _to_octal(char *buf, unsigned VALTYPE value,
return 1;
}
}
return (buf - buf0) + _to_x(buf, value, 8, precision);
return (buf - buf0) + _to_x(buf, value, 8);
}

static int _to_udec(char *buf, unsigned VALTYPE value, int precision)
static int _to_udec(char *buf, unsigned VALTYPE value)
{
return _to_x(buf, value, 10, precision);
return _to_x(buf, value, 10);
}

static int _to_dec(char *buf, VALTYPE value, bool fplus, bool fspace,
int precision)
static int _to_dec(char *buf, VALTYPE value, bool fplus, bool fspace)
{
char *start = buf;

Expand All @@ -140,7 +126,7 @@ static int _to_dec(char *buf, VALTYPE value, bool fplus, bool fspace,
*buf++ = ' ';
}

return (buf + _to_udec(buf, value, precision)) - start;
return (buf + _to_udec(buf, value)) - start;
}

static void _rlrshift(uint64_t *v)
Expand Down Expand Up @@ -451,15 +437,13 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
* has to be propagated across the file
*/
char buf[MAXFLD + 1];
int c;
char c;
int count;
char *cptr;
bool falt, fminus, fplus, fspace;
bool falt, fminus, fplus, fspace, fzero;
int i;
char pad;
int precision;
int prefix;
int width;
int width, precision;
int clen, prefix, zero_head;
VALTYPE val;

#define PUTC(c) do { if ((*func)(c, dest) == EOF) return EOF; } while (false)
Expand All @@ -471,9 +455,7 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
PUTC(c);
count++;
} else {
fminus = fplus = fspace = falt = false;
pad = ' '; /* Default pad character */

fminus = fplus = fspace = falt = fzero = false;
while (strchr("-+ #0", (c = *format++)) != NULL) {
switch (c) {
case '-':
Expand All @@ -493,7 +475,7 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
break;

case '0':
pad = '0';
fzero = true;
break;

case '\0':
Expand Down Expand Up @@ -560,8 +542,8 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
switch (c) {
case 'c':
buf[0] = va_arg(vargs, int);
c = 1;
pad = ' ';
clen = 1;
precision = 0;
break;

case 'd':
Expand All @@ -584,13 +566,10 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
val = va_arg(vargs, int);
break;
}
c = _to_dec(buf, val, fplus, fspace, precision);
clen = _to_dec(buf, val, fplus, fspace);
if (fplus || fspace || val < 0) {
prefix = 1;
}
if (precision >= 0) {
pad = ' ';
}
break;

case 'e':
Expand Down Expand Up @@ -620,11 +599,12 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
double_val = u.i;
#endif

c = _to_float(buf, double_val, c, falt, fplus,
fspace, precision);
clen = _to_float(buf, double_val, c, falt,
fplus, fspace, precision);
if (fplus || fspace || (buf[0] == '-')) {
prefix = 1;
}
precision = -1;
break;
}

Expand Down Expand Up @@ -655,10 +635,8 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)

case 'p':
val = (uintptr_t) va_arg(vargs, void *);
c = _to_hex(buf, val, true, 2*sizeof(void *), 'x');
if (precision >= 0) {
pad = ' ';
}
clen = _to_hex(buf, val, true, 'x');
prefix = 2;
break;

case 's':
Expand All @@ -667,12 +645,12 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
if (precision < 0) {
precision = INT_MAX;
}
for (c = 0; c < precision; c++) {
if (cptr[c] == '\0') {
for (clen = 0; clen < precision; clen++) {
if (cptr[clen] == '\0') {
break;
}
}
pad = ' ';
precision = 0;
break;

case 'o':
Expand All @@ -698,18 +676,15 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
break;
}
if (c == 'o') {
c = _to_octal(buf, val, falt, precision);
clen = _to_octal(buf, val, falt);
} else if (c == 'u') {
c = _to_udec(buf, val, precision);
clen = _to_udec(buf, val);
} else {
c = _to_hex(buf, val, falt, precision, c);
clen = _to_hex(buf, val, falt, c);
if (falt) {
prefix = 2;
}
}
if (precision >= 0) {
pad = ' ';
}
break;

case '%':
Expand All @@ -727,28 +702,42 @@ int z_prf(int (*func)(), void *dest, const char *format, va_list vargs)
return count;
}

if (precision >= 0) {
zero_head = precision - clen + prefix;
} else if (fzero) {
zero_head = width - clen;
} else {
zero_head = 0;
}
if (zero_head < 0) {
zero_head = 0;
}
width -= clen + zero_head;

/* padding for right justification */
if (!fminus && c < width) {
if (pad == ' ') {
prefix = 0;
}
width -= prefix;
c -= prefix;
count += prefix;
while (prefix-- > 0) {
PUTC(*cptr++);
}
width -= c;
if (!fminus && width > 0) {
count += width;
while (width-- > 0) {
PUTC(pad);
PUTC(' ');
}
}

/* data out */
width -= c;
count += c;
while (c-- > 0) {
/* data prefix */
clen -= prefix;
count += prefix;
while (prefix-- > 0) {
PUTC(*cptr++);
}

/* zero-padded head */
count += zero_head;
while (zero_head-- > 0) {
PUTC('0');
}

/* main data */
count += clen;
while (clen-- > 0) {
PUTC(*cptr++);
}

Expand Down

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