Field

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Field

Specifies field alignment.

Syntax

Type|Union typename Field = { 1 | 2 | 4 }
...
End Type|Union

Description

Field can be used to pack Types or Unions more tightly than the default layout. The most commonly used value is Field = 1, which causes the Type or Union to be packed as tightly as possible, without any padding bytes being added between the fields or at the end of the Type. Field can only be used to decrease field alignment, but it cannot be used to increase it. In order to add padding bytes, a Union with appropriate members could be used instead.

Remarks

Dialect Differences

• In the -lang qb dialect, the compiler assumes Field = 1 by default, if no other Field was specified, causing all structures to be tightly packed, without added padding, as in QB.

Differences from QB

• In QB Field was used to define fields in a file buffer at run time. This feature is not implemented in FB, so the keyword has been redefined. To define fields in a file buffer, Types must be used.

See also

• Type
• Union

Examples

Type bitmap_header Field = 1

    bfType          As UShort

    bfsize          As ULong

    bfReserved1     As UShort

    bfReserved2     As UShort

    bfOffBits       As ULong

    biSize          As ULong

    biWidth         As ULong

    biHeight        As ULong

    biPlanes        As UShort

    biBitCount      As UShort

    biCompression   As ULong

    biSizeImage     As ULong

    biXPelsPerMeter As ULong

    biYPelsPerMeter As ULong

    biClrUsed       As ULong

    biClrImportant  As ULong

End Type

Dim bmp_header As bitmap_header

'Open up bmp.bmp and get its header data:

'Note: Will not work without a bmp.bmp to load . . .

Open "bmp.bmp" For Binary As #1

    Get #1, , bmp_header

Close #1

Print bmp_header.biWidth, bmp_header.biHeight

Sleep

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Category: User Defined Types
Kind: type

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.