303 lines
8.3 KiB
C
303 lines
8.3 KiB
C
#include <math.h>
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#include <string.h>
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#include "nasal.h"
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#include "data.h"
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// The maximum number of significant (decimal!) figures in an IEEE
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// double.
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#define DIGITS 16
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// The minimum size we'll allocate for a string. Since a string
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// structure is already 12 bytes, and each naRef that points to it is
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// 8, there isn't much point in being stingy.
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#define MINLEN 16
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static int tonum(unsigned char* s, int len, double* result);
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static int fromnum(double val, unsigned char* s);
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int naStr_len(naRef s)
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{
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if(!IS_STR(s)) return 0;
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return s.ref.ptr.str->len;
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}
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char* naStr_data(naRef s)
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{
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if(!IS_STR(s)) return 0;
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return s.ref.ptr.str->data;
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}
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static void setlen(struct naStr* s, int sz)
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{
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int currSz, waste;
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sz += 1; // Allow for an extra nul terminator
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currSz = s->len+1 < MINLEN ? MINLEN : s->len+1;
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waste = currSz - sz; // how much extra if we don't reallocate?
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if(s->data == 0 || waste < 0 || waste > MINLEN) {
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naFree(s->data);
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s->data = naAlloc(sz < MINLEN ? MINLEN : sz);
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}
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s->len = sz - 1;
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s->data[s->len] = 0; // nul terminate
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}
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naRef naStr_fromdata(naRef dst, char* data, int len)
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{
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if(!IS_STR(dst)) return naNil();
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setlen(dst.ref.ptr.str, len);
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memcpy(dst.ref.ptr.str->data, data, len);
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return dst;
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}
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naRef naStr_concat(naRef dest, naRef s1, naRef s2)
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{
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struct naStr* dst = dest.ref.ptr.str;
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struct naStr* a = s1.ref.ptr.str;
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struct naStr* b = s2.ref.ptr.str;
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if(!(IS_STR(s1)&&IS_STR(s2)&&IS_STR(dest))) return naNil();
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setlen(dst, a->len + b->len);
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memcpy(dst->data, a->data, a->len);
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memcpy(dst->data + a->len, b->data, b->len);
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return dest;
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}
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naRef naStr_substr(naRef dest, naRef str, int start, int len)
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{
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struct naStr* dst = dest.ref.ptr.str;
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struct naStr* s = str.ref.ptr.str;
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if(!(IS_STR(dest)&&IS_STR(str))) return naNil();
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if(start + len > s->len) { dst->len = 0; dst->data = 0; return naNil(); }
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setlen(dst, len);
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memcpy(dst->data, s->data + start, len);
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return dest;
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}
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int naStr_equal(naRef s1, naRef s2)
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{
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struct naStr* a = s1.ref.ptr.str;
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struct naStr* b = s2.ref.ptr.str;
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if(a->data == b->data) return 1;
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if(a->len != b->len) return 0;
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if(memcmp(a->data, b->data, a->len) == 0) return 1;
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return 0;
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}
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naRef naStr_fromnum(naRef dest, double num)
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{
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struct naStr* dst = dest.ref.ptr.str;
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unsigned char buf[DIGITS+8];
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setlen(dst, fromnum(num, buf));
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memcpy(dst->data, buf, dst->len);
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return dest;
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}
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int naStr_parsenum(char* str, int len, double* result)
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{
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return tonum(str, len, result);
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}
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int naStr_tonum(naRef str, double* out)
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{
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return tonum(str.ref.ptr.str->data, str.ref.ptr.str->len, out);
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}
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int naStr_numeric(naRef str)
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{
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double dummy;
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return tonum(str.ref.ptr.str->data, str.ref.ptr.str->len, &dummy);
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}
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void naStr_gcclean(struct naStr* str)
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{
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if(str->len > MINLEN) {
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naFree(str->data);
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str->data = 0;
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}
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str->len = 0;
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}
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////////////////////////////////////////////////////////////////////////
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// Below is a custom double<->string conversion library. Why not
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// simply use sprintf and atof? Because they aren't acceptably
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// platform independant, sadly. I've seen some very strange results.
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// This works the same way everywhere, although it is tied to an
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// assumption of standard IEEE 64 bit floating point doubles.
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//
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// In practice, these routines work quite well. Testing conversions
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// of random doubles to strings and back, this routine is beaten by
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// glibc on roundoff error 23% of the time, beats glibc in 10% of
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// cases, and ties (usually with an error of exactly zero) the
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// remaining 67%.
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////////////////////////////////////////////////////////////////////////
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// Reads an unsigned decimal out of the scalar starting at i, stores
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// it in v, and returns the next index to start at. Zero-length
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// decimal numbers are allowed, and are returned as zero.
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static int readdec(unsigned char* s, int len, int i, double* v)
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{
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*v = 0;
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if(i >= len) return len;
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while(i < len && s[i] >= '0' && s[i] <= '9') {
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*v= (*v) * 10 + (s[i] - '0');
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i++;
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}
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return i;
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}
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// Reads a signed integer out of the string starting at i, stores it
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// in v, and returns the next index to start at. Zero-length
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// decimal numbers (and length-1 strings like '+') are allowed, and
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// are returned as zero.
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static int readsigned(unsigned char* s, int len, int i, double* v)
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{
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double sgn=1, val;
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if(i >= len) { *v = 0; return len; }
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if(s[i] == '+') { i++; }
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else if(s[i] == '-') { i++; sgn = -1; }
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i = readdec(s, len, i, &val);
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*v = sgn*val;
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return i;
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}
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// Integer decimal power utility, with a tweak that enforces
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// integer-exactness for arguments where that is possible.
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static double decpow(int exp)
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{
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double v = 1;
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int absexp;
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if(exp < 0 || exp >= DIGITS)
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return pow(10, exp);
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else
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absexp = exp < 0 ? -exp : exp;
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while(absexp--) v *= 10.0;
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return v;
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}
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static int tonum(unsigned char* s, int len, double* result)
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{
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int i=0, fraclen=0;
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double sgn=1, val, frac=0, exp=0;
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// Read the integer part
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i = readsigned(s, len, i, &val);
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if(val < 0) { sgn = -1; val = -val; }
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// Read the fractional part, if any
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if(i < len && s[i] == '.') {
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i++;
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fraclen = readdec(s, len, i, &frac) - i;
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i += fraclen;
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}
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// Read the exponent, if any
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if(i < len && (s[i] == 'e' || s[i] == 'E'))
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i = readsigned(s, len, i+1, &exp);
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// compute the result
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*result = sgn * (val + frac * decpow(-fraclen)) * decpow(exp);
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// if we didn't use the whole string, return failure
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if(i < len) return 0;
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return 1;
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}
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// Very simple positive (!) integer print routine. Puts the result in
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// s and returns the number of characters written. Does not null
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// terminate the result.
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static int decprint(int val, unsigned char* s)
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{
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int p=1, i=0;
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if(val == 0) { *s = '0'; return 1; }
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while(p <= val) p *= 10;
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p /= 10;
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while(p > 0) {
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int count = 0;
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while(val >= p) { val -= p; count++; }
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s[i++] = '0' + count;
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p /= 10;
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}
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return i;
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}
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// Takes a positive (!) floating point numbers, and returns exactly
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// DIGITS decimal numbers in the buffer pointed to by s, and an
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// integer exponent as the return value. For example, printing 1.0
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// will result in "1000000000000000" in the buffer and -15 as the
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// exponent. The caller can then place the floating point as needed.
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static int rawprint(double val, unsigned char* s)
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{
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int exponent = (int)floor(log10(val));
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double mantissa = val / pow(10, exponent);
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int i, c;
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for(i=0; i<DIGITS-1; i++) {
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int digit = (int)floor(mantissa);
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s[i] = '0' + digit;
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mantissa -= digit;
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mantissa *= 10.0;
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}
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// Round (i.e. don't floor) the last digit
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c = (int)floor(mantissa);
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if(mantissa - c >= 0.5) c++;
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if(c < 0) c = 0;
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if(c > 9) c = 9;
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s[i] = '0' + c;
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return exponent - DIGITS + 1;
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}
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static int fromnum(double val, unsigned char* s)
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{
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unsigned char raw[DIGITS];
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unsigned char* ptr = s;
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int exp, digs, i=0;
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// Handle negatives
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if(val < 0) { *ptr++ = '-'; val = -val; }
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// Exactly an integer is a special case
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if(val == (int)val) {
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ptr += decprint(val, ptr);
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*ptr = 0;
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return ptr - s;
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}
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// Get the raw digits
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exp = rawprint(val, raw);
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// Examine trailing zeros to get a significant digit count
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for(i=DIGITS-1; i>0; i--)
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if(raw[i] != '0') break;
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digs = i+1;
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if(exp > 0 || exp < -(DIGITS+2)) {
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// Standard scientific notation
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exp += DIGITS-1;
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*ptr++ = raw[0];
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if(digs > 1) {
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*ptr++ = '.';
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for(i=1; i<digs; i++) *ptr++ = raw[i];
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}
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*ptr++ = 'e';
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if(exp < 0) { exp = -exp; *ptr++ = '-'; }
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else { *ptr++ = '+'; }
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if(exp < 10) *ptr++ = '0';
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ptr += decprint(exp, ptr);
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} else if(exp < 1-DIGITS) {
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// Fraction with insignificant leading zeros
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*ptr++ = '0'; *ptr++ = '.';
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for(i=0; i<-(exp+DIGITS); i++) *ptr++ = '0';
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for(i=0; i<digs; i++) *ptr++ = raw[i];
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} else {
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// Integer part
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for(i=0; i<DIGITS+exp; i++) *ptr++ = raw[i];
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if(i < digs) {
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// Fraction, if any
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*ptr++ = '.';
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while(i<digs) *ptr++ = raw[i++];
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}
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}
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*ptr = 0;
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return ptr - s;
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}
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