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liquid/strftime/strftime.go
2017-07-11 10:23:57 -04:00

69 lines
1.9 KiB
Go

// Package strftime wraps the C stdlib strftime and strptime functions.
package strftime
/*
#include <stdlib.h>
#include <time.h>
#include <errno.h>
int read_errno() { return errno; }
*/
import "C"
import (
"syscall"
"time"
"unsafe"
)
// Note: The use of errno below is not thread-safe.
//
// Even if we added a mutex, it would not be thread-safe
// relative to other C stdlib calls that don't use that mutex.
//
// OTOH, I can't find a format string that C strftime thinks is illegal
// to test this with, so maybe this is a non-issue
// Strftime wraps the C Strftime function
func Strftime(format string, t time.Time) (string, error) {
var (
_, offset = t.Zone()
tz = t.Location()
secs = t.Sub(time.Date(1970, 1, 1, 0, 0, 0, 0, tz)).Seconds() - float64(offset)
tt = C.time_t(secs)
tm = C.struct_tm{}
cFormat = C.CString(format)
cOut [256]C.char
)
defer C.free(unsafe.Pointer(cFormat)) // nolint: gas
C.localtime_r(&tt, &tm)
size := C.strftime(&cOut[0], C.size_t(len(cOut)), cFormat, &tm)
if size == 0 {
// If size == 0 there *might* be an error.
if errno := C.read_errno(); errno != 0 {
return "", syscall.Errno(errno)
}
}
return C.GoString(&cOut[0]), nil
}
// Strptime wraps the C strptime function
// func Strptime(format, s string) (time.Time, error) {
// var (
// tm = C.struct_tm{}
// cFormat = C.CString(format)
// cin = C.CString(s)
// )
// defer C.free(unsafe.Pointer(cin)) // nolint: gas
// defer C.free(unsafe.Pointer(cFormat)) // nolint: gas
// ptr := C.strptime(cin, cFormat, &tm)
// if ptr == nil {
// var zero time.Time
// return zero, &time.ParseError{
// Layout: format,
// Value: s,
// LayoutElem: format,
// ValueElem: s,
// }
// }
// return time.Date(int(tm.tm_year)+1900, time.Month(tm.tm_mon+1), int(tm.tm_mday), int(tm.tm_hour), int(tm.tm_min), int(tm.tm_sec), 0, time.UTC), nil
// }