Generic FileFormat Data Types: Difference between revisions

Revision as of 06:29, 3 August 2009

This is a generic list of data types encountered in all file formats. Not all of which will be used in a specific file format.

They are listed here, rather than repetitive typing in each of file format's documentation.

Little endian byte order, lsb first for numeric values, text is stored in Big endian byte order.

Type	Description
byte	8 bit (1 byte)
tbool	byte (0 = false).
short	16 bit signed short (2 bytes)
ushort	16 bit unsigned short (2 bytes)
long	32 bit signed integer (4 bytes)
ulong	32 bit unsigned integer (4 bytes)
float	32 bit signed single precision floating point value (4 bytes)
double	64 bit signed single precision floating point value (8 bytes)
asciiz	Null terminated (0x00) variable length ascii string
ascii	fixed length ascii string(UTF-8)

XYZTriplet
{
 float    x,y,z;
}

Note that 'int' is not used in this documentation for the following reasons:

an 'int' is machine and compiler and language dependent. It is an arbitrary size SIGNED value.
with exceptions, BI use floats when requiring negative values.
almost all references to 'integers' in BI file formats are either positive-only offsets into memory, zero based indexes, and counts.

the incidence of true shorts and true integers in BI is quite rare. Exception -1 is a favourite, to indicate default

@@ Line 14: / Line 14: @@
 |-
 |align="left"|byte||align="left"| 8 bit (1 byte)
+|-
+|align="middle"|tbool||align="left"| byte (0 = false).
 |-
 |align="middle"|short||align="left"| 16 bit signed short (2 bytes)
 |-
 |align="middle"|ushort||align="left"| 16 bit '''unsigned''' short (2 bytes)
+|-
+|align="middle"|long||align="left"| 32 bit signed integer (4 bytes)
 |-
 |align="middle"|ulong||align="left"| 32 bit '''unsigned''' integer (4 bytes)
@@ Line 31: / Line 35: @@
 |-
 |}
+====XYZTriplet====
+ XYZTriplet
+ {
+  float    x,y,z;
+ }
+:Note that 'int' is not used in this documentation for the following reasons:
-Note that the use of the word 'int' is bad policy. An int is machine and compiler and language dependent. BI use floats to represent signed values unsigned integers for indexes and string counts.
+:*an 'int' is machine and compiler and language dependent. It is an arbitrary size SIGNED value.
+:*with exceptions, BI use floats when requiring negative values.
+:*almost all references to 'integers' in BI file formats are either positive-only offsets into memory, zero based indexes, and counts.
+:the incidence of true shorts and true integers in BI is quite rare. Exception -1 is a favourite, to indicate default