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New private API functions _PyFloat_{Pack,Unpack}(4,8}. This is a
refactoring to get all the duplicates of this delicate code out of the cPickle and struct modules.
This commit is contained in:
Tim Peters
parent
d50ade68ec
commit
9905b943f7
4 changed files with 382 additions and 446 deletions
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@ -185,301 +185,27 @@ get_ulonglong(PyObject *v, unsigned LONG_LONG *p)
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/* Floating point helpers */
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/* These use ANSI/IEEE Standard 754-1985 (Standard for Binary Floating
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Point Arithmetic). See the following URL:
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http://www.psc.edu/general/software/packages/ieee/ieee.html */
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/* XXX Inf/NaN are not handled quite right (but underflow is!) */
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static int
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pack_float(double x, /* The number to pack */
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char *p, /* Where to pack the high order byte */
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int incr) /* 1 for big-endian; -1 for little-endian */
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{
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int s;
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int e;
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double f;
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long fbits;
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if (x < 0) {
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s = 1;
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x = -x;
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}
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else
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s = 0;
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f = frexp(x, &e);
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/* Normalize f to be in the range [1.0, 2.0) */
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if (0.5 <= f && f < 1.0) {
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f *= 2.0;
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e--;
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}
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else if (f == 0.0) {
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e = 0;
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}
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else {
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PyErr_SetString(PyExc_SystemError,
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"frexp() result out of range");
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return -1;
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}
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if (e >= 128)
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goto Overflow;
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else if (e < -126) {
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/* Gradual underflow */
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f = ldexp(f, 126 + e);
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e = 0;
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}
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else if (!(e == 0 && f == 0.0)) {
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e += 127;
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f -= 1.0; /* Get rid of leading 1 */
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}
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f *= 8388608.0; /* 2**23 */
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fbits = (long) floor(f + 0.5); /* Round */
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assert(fbits <= 8388608);
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if (fbits >> 23) {
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/* The carry propagated out of a string of 23 1 bits. */
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fbits = 0;
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++e;
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if (e >= 255)
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goto Overflow;
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}
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/* First byte */
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*p = (s<<7) | (e>>1);
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p += incr;
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/* Second byte */
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*p = (char) (((e&1)<<7) | (fbits>>16));
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p += incr;
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/* Third byte */
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*p = (fbits>>8) & 0xFF;
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p += incr;
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/* Fourth byte */
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*p = fbits&0xFF;
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/* Done */
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return 0;
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Overflow:
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PyErr_SetString(PyExc_OverflowError,
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"float too large to pack with f format");
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return -1;
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}
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static int
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pack_double(double x, /* The number to pack */
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char *p, /* Where to pack the high order byte */
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int incr) /* 1 for big-endian; -1 for little-endian */
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{
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int s;
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int e;
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double f;
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long fhi, flo;
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if (x < 0) {
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s = 1;
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x = -x;
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}
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else
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s = 0;
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f = frexp(x, &e);
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/* Normalize f to be in the range [1.0, 2.0) */
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if (0.5 <= f && f < 1.0) {
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f *= 2.0;
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e--;
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}
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else if (f == 0.0) {
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e = 0;
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}
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else {
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PyErr_SetString(PyExc_SystemError,
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"frexp() result out of range");
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return -1;
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}
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if (e >= 1024)
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goto Overflow;
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else if (e < -1022) {
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/* Gradual underflow */
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f = ldexp(f, 1022 + e);
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e = 0;
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}
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else if (!(e == 0 && f == 0.0)) {
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e += 1023;
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f -= 1.0; /* Get rid of leading 1 */
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}
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/* fhi receives the high 28 bits; flo the low 24 bits (== 52 bits) */
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f *= 268435456.0; /* 2**28 */
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fhi = (long) floor(f); /* Truncate */
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assert(fhi < 268435456);
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f -= (double)fhi;
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f *= 16777216.0; /* 2**24 */
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flo = (long) floor(f + 0.5); /* Round */
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assert(flo <= 16777216);
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if (flo >> 24) {
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/* The carry propagated out of a string of 24 1 bits. */
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flo = 0;
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++fhi;
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if (fhi >> 28) {
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/* And it also progagated out of the next 28 bits. */
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fhi = 0;
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++e;
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if (e >= 2047)
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goto Overflow;
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}
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}
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/* First byte */
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*p = (s<<7) | (e>>4);
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p += incr;
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/* Second byte */
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*p = (char) (((e&0xF)<<4) | (fhi>>24));
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p += incr;
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/* Third byte */
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*p = (fhi>>16) & 0xFF;
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p += incr;
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/* Fourth byte */
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*p = (fhi>>8) & 0xFF;
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p += incr;
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/* Fifth byte */
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*p = fhi & 0xFF;
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p += incr;
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/* Sixth byte */
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*p = (flo>>16) & 0xFF;
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p += incr;
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/* Seventh byte */
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*p = (flo>>8) & 0xFF;
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p += incr;
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/* Eighth byte */
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*p = flo & 0xFF;
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p += incr;
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/* Done */
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return 0;
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Overflow:
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PyErr_SetString(PyExc_OverflowError,
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"float too large to pack with d format");
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return -1;
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}
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static PyObject *
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unpack_float(const char *p, /* Where the high order byte is */
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int incr) /* 1 for big-endian; -1 for little-endian */
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unpack_float(const char *p, /* start of 4-byte string */
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int le) /* true for little-endian, false for big-endian */
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{
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int s;
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int e;
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long f;
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double x;
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/* First byte */
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s = (*p>>7) & 1;
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e = (*p & 0x7F) << 1;
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p += incr;
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/* Second byte */
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e |= (*p>>7) & 1;
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f = (*p & 0x7F) << 16;
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p += incr;
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/* Third byte */
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f |= (*p & 0xFF) << 8;
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p += incr;
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/* Fourth byte */
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f |= *p & 0xFF;
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x = (double)f / 8388608.0;
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/* XXX This sadly ignores Inf/NaN issues */
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if (e == 0)
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e = -126;
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else {
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x += 1.0;
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e -= 127;
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}
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x = ldexp(x, e);
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if (s)
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x = -x;
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x = _PyFloat_Unpack4((unsigned char *)p, le);
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if (x == -1.0 && PyErr_Occurred())
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return NULL;
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return PyFloat_FromDouble(x);
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}
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static PyObject *
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unpack_double(const char *p, /* Where the high order byte is */
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int incr) /* 1 for big-endian; -1 for little-endian */
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unpack_double(const char *p, /* start of 8-byte string */
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int le) /* true for little-endian, false for big-endian */
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{
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int s;
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int e;
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long fhi, flo;
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double x;
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/* First byte */
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s = (*p>>7) & 1;
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e = (*p & 0x7F) << 4;
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p += incr;
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/* Second byte */
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e |= (*p>>4) & 0xF;
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fhi = (*p & 0xF) << 24;
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p += incr;
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/* Third byte */
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fhi |= (*p & 0xFF) << 16;
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p += incr;
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/* Fourth byte */
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fhi |= (*p & 0xFF) << 8;
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p += incr;
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/* Fifth byte */
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fhi |= *p & 0xFF;
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p += incr;
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/* Sixth byte */
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flo = (*p & 0xFF) << 16;
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p += incr;
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/* Seventh byte */
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flo |= (*p & 0xFF) << 8;
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p += incr;
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/* Eighth byte */
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flo |= *p & 0xFF;
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p += incr;
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x = (double)fhi + (double)flo / 16777216.0; /* 2**24 */
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x /= 268435456.0; /* 2**28 */
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/* XXX This sadly ignores Inf/NaN */
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if (e == 0)
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e = -1022;
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else {
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x += 1.0;
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e -= 1023;
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}
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x = ldexp(x, e);
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if (s)
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x = -x;
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x = _PyFloat_Unpack8((unsigned char *)p, le);
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if (x == -1.0 && PyErr_Occurred())
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return NULL;
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return PyFloat_FromDouble(x);
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}
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@ -887,13 +613,13 @@ bu_ulonglong(const char *p, const formatdef *f)
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static PyObject *
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bu_float(const char *p, const formatdef *f)
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{
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return unpack_float(p, 1);
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return unpack_float(p, 0);
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}
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static PyObject *
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bu_double(const char *p, const formatdef *f)
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{
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return unpack_double(p, 1);
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return unpack_double(p, 0);
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}
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static int
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@ -967,7 +693,7 @@ bp_float(char *p, PyObject *v, const formatdef *f)
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"required argument is not a float");
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return -1;
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}
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return pack_float(x, p, 1);
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return _PyFloat_Pack4(x, (unsigned char *)p, 0);
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}
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static int
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@ -979,7 +705,7 @@ bp_double(char *p, PyObject *v, const formatdef *f)
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"required argument is not a float");
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return -1;
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}
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return pack_double(x, p, 1);
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return _PyFloat_Pack8(x, (unsigned char *)p, 0);
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}
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static formatdef bigendian_table[] = {
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@ -1053,13 +779,13 @@ lu_ulonglong(const char *p, const formatdef *f)
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static PyObject *
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lu_float(const char *p, const formatdef *f)
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{
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return unpack_float(p+3, -1);
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return unpack_float(p, 1);
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}
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static PyObject *
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lu_double(const char *p, const formatdef *f)
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{
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return unpack_double(p+7, -1);
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return unpack_double(p, 1);
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}
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static int
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@ -1133,7 +859,7 @@ lp_float(char *p, PyObject *v, const formatdef *f)
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"required argument is not a float");
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return -1;
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}
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return pack_float(x, p+3, -1);
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return _PyFloat_Pack4(x, (unsigned char *)p, 1);
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}
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static int
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@ -1145,7 +871,7 @@ lp_double(char *p, PyObject *v, const formatdef *f)
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"required argument is not a float");
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return -1;
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}
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return pack_double(x, p+7, -1);
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return _PyFloat_Pack8(x, (unsigned char *)p, 1);
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}
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static formatdef lilendian_table[] = {
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