add scan_httpdate

CHANGES

@@ -12,7 +12,7 @@
   add stralloc versions of textcode API (Kai Ruemmler)
   add html to textcode ('<' to '&lt;' etc)
   add fmt_human and fmt_humank (format numbers ala ls -H/-h)
-  add fmt_httpdate
+  add fmt_httpdate and scan_httpdate
 
 0.14:
   avoid bus errors in byte_copy

scan.h

@@ -1,6 +1,8 @@
 #ifndef SCAN_H
 #define SCAN_H
 
+#include <sys/types.h>
+
 #ifdef __dietlibc__
 #include <sys/cdefs.h>
 #endif
@@ -58,4 +60,12 @@ extern unsigned int scan_charsetnskip(const char *in,const char *charset,unsigne
  * charset (ASCIIZ string) for all 0<=i<=n */
 extern unsigned int scan_noncharsetnskip(const char *in,const char *charset,unsigned int limit) __pure__;
 
+/* try to parse ASCII GMT date; does not understand time zones. */
+/* example dates:
+ *   "Sun, 06 Nov 1994 08:49:37 GMT"
+ *   "Sunday, 06-Nov-94 08:49:37 GMT"
+ *   "Sun Nov  6 08:49:37 1994"
+ */
+extern unsigned int scan_httpdate(const char *in,time_t *t) __pure__;
+
 #endif

scan/scan_httpdate.3

@@ -0,0 +1,15 @@
+.TH scan_httpdate 3
+.SH NAME
+scan_httpdate \- parse a HTTP date
+.SH SYNTAX
+.B #include <scan.h>
+
+int \fBscan_httpdate\fP(const char *\fIsrc\fR,time_t *\fIdest\fR);
+.SH DESCRIPTION
+scan_httpdate parses a date as defined in the HTTP standard into a
+time_t.  It returns the number of bytes read from \fIsrc\fR (0 for parse
+error).
+
+The only supported time zone is GMT.
+.SH "SEE ALSO"
+fmt_httpdate(3)

scan/scan_httpdate.c

@@ -0,0 +1,59 @@
+#include "scan.h"
+#include "byte.h"
+#include "case.h"
+#include <time.h>
+
+static int parsetime(const char*c,struct tm* x) {
+  unsigned long tmp;
+  c+=scan_ulong(c,&tmp); x->tm_hour=tmp;
+  if (*c!=':') return -1; ++c;
+  c+=scan_ulong(c,&tmp); x->tm_min=tmp;
+  if (*c!=':') return -1; ++c;
+  c+=scan_ulong(c,&tmp); x->tm_sec=tmp;
+  if (*c!=' ') return -1;
+  return 0;
+}
+
+unsigned int scan_httpdate(const char *in,time_t *t) {
+  struct tm x;
+  int i;
+  unsigned long tmp;
+  const char* c;
+  static const char months[] = "JanFebMarAprMayJunJulAugSepOctNovDec";
+  if (!(c=in)) return 0;
+  if (c[3]==',') c+=5; else
+  if (c[6]==',') c+=8; else {
+    c+=4;
+    for (i=0; i<12; ++i) {
+      if (case_equalb(c,3,months+i*3)) {
+	x.tm_mon=i; break;
+      }
+    }
+    c+=4; if (*c==' ') ++c;
+    c+=scan_ulong(c,&tmp); x.tm_mday=tmp;
+    ++c;
+    if (parsetime(c,&x)) return 0;
+    c+=9;
+    c+=scan_ulong(c,&tmp); x.tm_year=tmp-1900;
+    goto done;
+  }
+  c+=scan_ulong(c,&tmp); x.tm_mday=tmp;
+  ++c;
+  for (i=0; i<12; ++i)
+    if (case_equalb(c,3,months+i*3)) {
+      x.tm_mon=i; break;
+    }
+  c+=4;
+  c+=scan_ulong(c,&tmp);
+  if (tmp>1000) x.tm_year=tmp-1900; else
+    if (tmp<70) x.tm_year=tmp+100; else
+                x.tm_year=tmp;
+  ++c;
+  if (parsetime(c,&x)) return 0;
+  c+=9;
+  if (byte_equal(c,3,"GMT")) c+=3;
+done:
+  x.tm_wday=x.tm_yday=x.tm_isdst=0;
+  *t=mktime(&x);
+  return c-in;
+}

test/fmt_httpdate.c

@@ -1,8 +1,16 @@
 #include <time.h>
+#include <scan.h>
 #include <buffer.h>
 
 main() {
   char buf[100];
-  buffer_put(buffer_1,buf,fmt_httpdate(buf,time(0)));
+  time_t s,t;
+  buffer_put(buffer_1,buf,fmt_httpdate(buf,time(&s)));
+  buffer_putnlflush(buffer_1);
+  buffer_puts(buffer_1,buf+scan_httpdate(buf,&t));
+  buffer_putnlflush(buffer_1);
+  buffer_putulong(buffer_1,s);
+  buffer_puts(buffer_1," vs. ");
+  buffer_putulong(buffer_1,t);
   buffer_putnlflush(buffer_1);
 }