Nondestructive Read (Device-Driver Function 05h)

NDREADREQUEST STRUC

nrrLength db ? ;length of record, in bytes

nrrUnit db ? ;not used

nrrFunction db 05h ;function number

nrrStatus dw ? ;status

nrrReserved db 8 dup(?) ;reserved

nrrChar db ? ;OUTPUT: character read from device

NDREADREQUEST ENDS

Nondestructive Read (Device-Driver Function 05h) returns the next character from the input buffer without removing it from the buffer; subsequent read operations should return the same character.

This function is required for character-device drivers only.

Fields

nrrLength

Specifies the length, in bytes, of the NDREADREQUEST structure.

nrrUnit

Not used.

nrrFunction

Specifies the Nondestructive Read function: 05h.

nrrStatus

Specifies the status of the completed function. If the device input buffer has at least one character, the busy bit (bit 9) must be zero, indicating that MS-DOS need not wait to read a character. If the input buffer has no characters, the driver must set the busy bit. In both cases, the driver must set the done bit (bit 8).

If the function is not successful, the driver must set both the error and done bits (bits 15 and 8) and copy an error value to the low-order byte.

nrrReserved

Reserved; do not use.

nrrChar

Receives the next character in the input buffer. The driver must copy the character without removing it from the input buffer.

See Also

Device-Driver Function 04h Read