Apple-2gs-SW/ORCALib
1
0
Fork 0
mirror of https://github.com/byteworksinc/ORCALib.git synced 2025-04-13 07:37:09 +00:00
Code Issues Projects Releases Wiki Activity

Fix bug with fseek(..., SEEK_CUR) on read-only streams.

Browse Source 
This would seek to the wrong location, and in some cases try to seek before the beginning of the file, leading to an error condition.

The problem stemmed from fseek calling fflush, which sets up the stream's buffer state in a way appropriate for writing but not for reading. It then calls ftell, which (for a read-only stream) would misinterpret this state and miscalculate the current position.

The fix is to make fflush work correctly on a read-only stream, setting up the state for reading. (User code calling fflush on a read-only stream would be undefined behavior, but since fseek does it we need to make it work.)

This fixes #6.
This commit is contained in:
Stephen Heumann 2022-06-25 21:37:47 -05:00
parent 3581d20a7c
commit 0047b755c9
1 changed files with 10 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
stdio.asm
View File

@ -4484,7 +4484,7 @@ orVal ds 2 for setting the case of characters
iny
txa
sta [stream],Y
ldy #FILE_base set the end of buffer mark
ldy #FILE_base set the end of buffer mark
lda [stream],Y
ldy #FILE_size
clc
@ -4500,13 +4500,20 @@ orVal ds 2 for setting the case of characters
dey
dey
sta [stream],Y
ldy #FILE_size set the number of chars the buffer
ldy #FILE_flag if read stream
lda [stream],Y
bit _IOREAD
beq ib1
lda #0 set count of chars in buffer to 0
tax
bra ib2 else
ib1 ldy #FILE_size set the number of chars the buffer
lda [stream],Y can hold
tax
iny
iny
lda [stream],Y
ldy #FILE_cnt+2
ib2 ldy #FILE_cnt+2
sta [stream],Y
dey
dey