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package libc
/*
#define _POSIX_SOURCE
#include <stdlib.h>
#include <time.h>
*/
import "C"
import (
"time"
"unsafe"
)
type Tm struct {
core C.struct_tm
}
func (tm Tm) native() *C.struct_tm {
return &tm.core
}
func NewTm(t time.Time) Tm {
var tm C.struct_tm
tm.tm_sec = C.int(t.Second())
tm.tm_min = C.int(t.Minute())
tm.tm_hour = C.int(t.Hour())
tm.tm_mday = C.int(t.Day())
tm.tm_mon = C.int(t.Month() - 1)
tm.tm_year = C.int(t.Year() - 1900)
tm.tm_wday = C.int(t.Weekday())
tm.tm_yday = C.int(t.YearDay() - 1)
tm.tm_isdst = -1
return Tm{
core: tm,
}
}
const initialBufSize = 256
func Strftime(format string, tm Tm) (s string) {
if format == "" {
return
}
fmt := C.CString(format)
defer C.free(unsafe.Pointer(fmt))
for size := initialBufSize; ; size *= 2 {
buf := (*C.char)(C.malloc(C.size_t(size))) // can panic
defer C.free(unsafe.Pointer(buf))
n := C.strftime(buf, C.size_t(size), fmt, tm.native())
if n == 0 {
// strftime(3), unhelpfully: "Note that the return value 0 does not
// necessarily indicate an error; for example, in many locales %p
// yields an empty string." This leaves no definite way to
// distinguish between the cases where the value doesn't fit and
// where it does because the string is empty. In the latter case,
// allocating increasingly larger buffers will never change the
// result, so we need some heuristic for bailing out.
//
// Since a single 2-byte conversion sequence should not produce an
// output longer than about 24 bytes, we conservatively allow the
// buffer size to grow up to 20 times larger than the format string
// before giving up.
if size > 20*len(format) {
return
}
} else if int(n) < size {
s = C.GoStringN(buf, C.int(n))
return
}
}
}
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