Fast parsing of datetime strings (like YYYYMMDDHHMMSS)
Posted: Sat Aug 20, 2016 8:33 am
Not as flexible as ParseDate since the offset of each component is hard coded
but the code is easy to adapt to a format like YYYY-MM-DD HH:MM:SS .
You have to make sure yourself the strings contain valid information; no checks are performed. The focus is on speed.
It's much faster as the PB procedure ParseDate and returns a quad value so no problem with dates beyond 2037.
but the code is easy to adapt to a format like YYYY-MM-DD HH:MM:SS .
You have to make sure yourself the strings contain valid information; no checks are performed. The focus is on speed.
It's much faster as the PB procedure ParseDate and returns a quad value so no problem with dates beyond 2037.
Code: Select all
#DT_Unicode = #True; set to #False for parsing Ascii strings
Macro GetDigits(reg, pos)
CompilerIf #DT_Unicode
CompilerIf #PB_Compiler_Processor = #PB_Processor_x64
!mov reg, [r8 + pos * 2]
CompilerElse
!mov reg, [esi + pos * 2]
CompilerEndIf
!sub reg, 0x00300030
!imul reg, 0x0a000100
CompilerElse
CompilerIf #PB_Compiler_Processor = #PB_Processor_x64
!movzx reg, word [r8 + pos]
CompilerElse
!movzx reg, word [esi + pos]
CompilerEndIf
!sub reg, 0x00003030
!imul reg, 0x0a010000
CompilerEndIf
!shr reg, 24
EndMacro
Procedure.q ParseDateTimeStamp(*dt) ; yyyymmddhhiiss
CompilerIf #PB_Compiler_Processor = #PB_Processor_x64
!mov r8, [p.p_dt]
!lea r9, [pdts_month_table]
CompilerElse
!mov eax, [p.p_dt]
!push esi
!mov esi, eax
CompilerEndIf
; *** get date part ***
GetDigits(ecx, 0); years (first two digits)
!imul eax, ecx, 36524
!shl ecx, 8
GetDigits(edx, 2); years (last two digits)
!or ecx, edx
!imul edx, 365
!add eax, edx
GetDigits(edx, 4); months
!and edx, 15
; leap correction
!cmp edx, 3
!sbb ecx, 0xfffffc00
!and ecx, 0x0000fcff
!bt ecx, 7
!adc ch, cl
!shr ecx, 10
!add eax, ecx
; lookup and add month offset
CompilerIf #PB_Compiler_Processor = #PB_Processor_x64
!movsx ecx, word [r9 + rdx * 2]
CompilerElse
!movsx ecx, word [pdts_month_table + edx * 2]
CompilerEndIf
!add eax, ecx
; add days
GetDigits(ecx, 6); days
!add eax, ecx
; *** get time part ***
GetDigits(ecx, 8); hours
!imul ecx, 3600
GetDigits(edx, 10); minutes
!imul edx, 60
!add ecx, edx
GetDigits(edx, 12); seconds
!add ecx, edx
; combine days and seconds and return result
!sub eax, 0xafaa9; 1/1/1970 offset (use 0xb2576 for 1/1/2000 offset)
!mov edx, 86400
!imul edx
CompilerIf #PB_Compiler_Processor = #PB_Processor_x64
!shl rdx, 32
!or rax, rdx
!add rax, rcx
CompilerElse
!add eax, ecx
!adc edx, 0
!pop esi
CompilerEndIf
ProcedureReturn
!pdts_month_table:
!dw 0,0,31,59,90,120,151,181,212,243,273,304,334,0,0,0
EndProcedure