83Plus:Software:usb8x/Asm Interface/MSD/DOS fileRead

Synopsis

Name: DOS_fileRead

Minimum usb8x version: 0.10

Reads bytes from an open file at current seek offset.

Inputs

• HL points to file handle of an opened file
• DE points to a buffer to store the bytes read
• BC is the number of bytes to read

Outputs

• BC is the number of bytes actually read
• C set if problems or encountered end-of-file first

Destroys

• AF, BC, DE, HL

Notes

Bit 1 of the 22nd byte (offset 21) of the file handle will be set if the end of the file was reached. Example code to read 10 bytes to statVars:

ld hl,file_handle
ld de,statVars
ld bc,10
U_CALL DOS_fileRead
ld a,(file_handle+21)
and 00000010b
jr nz,eofReached
...

eofReached:

...

See Also

• [[../DOS_fileWrite|DOS_fileWrite]] - Writes bytes to a file and grows it if necessary