Change a byte in memory

[SPH]

Code: Select all

UseJPEGImageDecoder()

file$ = OpenFileRequester("Sélectionnez un fichier","","JPG (.jpg)|*.jpg|All files (*.*)|*.*",0)
  If file$
    If ReadFile(0, file$) 
      length = Lof(0)                            ; Lit la taille en octets du fichier 
      *MemoryID = AllocateMemory(length)         ; alloue un bloc mémoire de la taille du fichier
      If *MemoryID
        bytes = ReadData(0, *MemoryID, length)   ; Lit les données du fichier et les place dans le bloc mémoire
      EndIf
      CloseFile(0)
    EndIf
  EndIf
  
  Resultat = CatchImage(0, *MemoryID, length)
 

I want to delete the first byte on the memoryID
What is the instruction ?

[Peyman]

you can use pokeB to set the first byte null :

Code: Select all

PokeB(*MemoryID, 0)

[STARGÅTE]

Or you can use a Byte-Array like:

Code: Select all

Structure ByteArray
	b.b[0]
EndStructure

Define Text.s = "Some Text"
Define *MemoryID.ByteArray = @Text

; change a byte 
*MemoryID\b[4] = '!'

Debug Text

[tinman]

Even if you set the first byte to null you'd have to change the address you use in the call to CatchImage() to be "*MemoryID + 1" and reduce length by 1, otherwise it would not be a correctly formatted JPEG image in memory.

Why not just read only what you need?

Code: Select all

UseJPEGImageDecoder()

file$ = OpenFileRequester("Sélectionnez un fichier","","JPG (.jpg)|*.jpg|All files (*.*)|*.*",0)
  If file$
    If ReadFile(0, file$)
      length = Lof(0) - 1                            ; Lit la taille en octets du fichier
      *MemoryID = AllocateMemory(length)         ; alloue un bloc mémoire de la taille du fichier
      If *MemoryID
        FileSeek(0, 1)
        bytes = ReadData(0, *MemoryID, length)   ; Lit les données du fichier et les place dans le bloc mémoire
      EndIf
      CloseFile(0)
    EndIf
  EndIf
 
  Resultat = CatchImage(0, *MemoryID, length)

[SPH]

Ho, thx

[epidemicz]

Or you can use a Byte-Array like:

Code: Select all

Structure ByteArray
	b.b[0]
EndStructure

Define Text.s = "Some Text"
Define *MemoryID.ByteArray = @Text

; change a byte 
*MemoryID\b[4] = '!'

Debug Text

Wow, that's a great example, much more elegant than what would have done :/

Code: Select all

Define Text.s = "Some Text"
Define *MemoryID = @Text

; change a byte
PokeC(*MemoryID+4, Asc("!"))

Debug Text