7.26 SYS_WRITE (0x05)

Writes the contents of a buffer to a specified file at the current file position.

The file position is specified either:

  • explicitly, by a SYS_SEEK

  • implicitly as one byte beyond the previous SYS_READ or SYS_WRITE request.

The file position is at the start of the file when the file is opened, and is lost when the file is closed.

Perform the file operation as a single action whenever possible. For example, do not split a write of 16KB into four 4KB chunks unless there is no alternative.

Entry

On entry, R1 contains a pointer to a three-word data block:

word 1

contains a handle for a file previously opened with SYS_OPEN

word 2

points to the memory containing the data to be written

word 3

contains the number of bytes to be written from the buffer to the file.

Return

On exit, R0 contains:

  • 0 if the call is successful

  • the number of bytes that are not written, if there is an error.

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