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Deprecate file-read-chunks by incorporating it inside asma.
This commit is contained in:
Andrew Alderwick
parent
60f04ca053
commit
113220b10d
2 changed files with 53 additions and 210 deletions
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@ -230,7 +230,59 @@
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POP2 POP2 POP2 POP2 POP2
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JMP2r
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~projects/library/file-read-chunks.tal
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@file-read-chunks ( func* udata* buf* size* filename* -- func* udata'* buf* size* filename* )
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#0000 DUP2 ( F* U* B* SZ* FN* OL* OH* / )
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&resume
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ROT2 STH2 ( F* U* B* SZ* OL* OH* / FN* )
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ROT2 ( F* U* B* OL* OH* SZ* / FN* )
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&loop
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STH2kr .File/name DEO2 ( F* U* B* OL* OH* SZ* / FN* )
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STH2k ,ffwd/length STR2 ( F* U* B* OL* OH* / FN* SZ* )
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STH2 ( F* U* B* OL* / FN* SZ* OH* )
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STH2k ,ffwd/offset STR2 ( F* U* B* / FN* SZ* OH* OL* )
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DUP2 ,ffwd/addr STR2
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,ffwd JSR
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SWP2 ( F* B* U* / FN* SZ* OH* OL* )
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ROT2k NIP2 ( F* B* U* B* F* / FN* SZ* OH* OL* )
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OVR2 .File/read DEO2 ( F* B* U* B* F* / FN* SZ* OH* OL* )
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.File/success DEI2 SWP2 ( F* B* U* B* length* F* / FN* SZ* OH* OL* )
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JSR2 ( F* B* U'* done-up-to* / FN* SZ* OH* OL* )
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ROT2 SWP2 ( F* U'* B* done-up-to* / FN* SZ* OH* OL* )
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SUB2k NIP2 ( F* U'* B* -done-length* / FN* SZ* OH* OL* )
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ORAk ,¬-end JCN ( F* U'* B* -done-length* / FN* SZ* OH* OL* )
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POP2 POP2r POP2r ( F* U'* B* / FN* SZ* )
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STH2r STH2r ( F* U'* B* SZ* FN* / )
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JMP2r
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¬-end
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STH2r SWP2 ( F* U'* B* OL* -done-length* / FN* SZ* OH* )
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LTH2k JMP INC2r ( F* U'* B* OL* -done-length* / FN* SZ* OH'* )
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SUB2 ( F* U'* B* OL'* / FN* SZ* OH'* )
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STH2r STH2r ( F* U'* B* OL'* OH'* SZ* / FN* )
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,&loop JMP
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@ffwd
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LIT2 &length $2
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LIT2 &offset $2
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&coarse ( length* offset* )
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GTH2k ,&fine JCN
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OVR2 .File/length DEO2
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,&addr LDR2 .File/read DEO2
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OVR2 SUB2
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,&coarse JMP
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&fine ( length* offset* )
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.File/length DEO2 ( length* )
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,&addr LDR2 .File/read DEO2
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.File/length DEO2 ( )
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JMP2r
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&addr $2
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(
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Assemble a chunk of source code, which begins with whitespace or the start
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@ -1,209 +0,0 @@
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(
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# Summary
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*** CAUTION: this library is deprecated! ***
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Chunked file reads are now possible in the File device directly: just use
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File/read or File/write multiple times. This library exists for compatibility to
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keep asma going until it gets a more substantial rewrite.
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***
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Reads a file in chunks - perfect for when you have a small buffer or when you
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don't know the file size. Copes with files up to 4,294,967,295 bytes long.
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# Code
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)
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@file-read-chunks ( func* udata* buf* size* filename* -- func* udata'* buf* size* filename* )
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#0000 DUP2 ( F* U* B* SZ* FN* OL* OH* / )
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&resume
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ROT2 STH2 ( F* U* B* SZ* OL* OH* / FN* )
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ROT2 ( F* U* B* OL* OH* SZ* / FN* )
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&loop
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STH2kr .File/name DEO2 ( F* U* B* OL* OH* SZ* / FN* )
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STH2k ,ffwd/length STR2 ( F* U* B* OL* OH* / FN* SZ* )
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STH2 ( F* U* B* OL* / FN* SZ* OH* )
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STH2k ,ffwd/offset STR2 ( F* U* B* / FN* SZ* OH* OL* )
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DUP2 ,ffwd/addr STR2
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,ffwd JSR
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SWP2 ( F* B* U* / FN* SZ* OH* OL* )
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ROT2k NIP2 ( F* B* U* B* F* / FN* SZ* OH* OL* )
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OVR2 .File/read DEO2 ( F* B* U* B* F* / FN* SZ* OH* OL* )
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.File/success DEI2 SWP2 ( F* B* U* B* length* F* / FN* SZ* OH* OL* )
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JSR2 ( F* B* U'* done-up-to* / FN* SZ* OH* OL* )
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ROT2 SWP2 ( F* U'* B* done-up-to* / FN* SZ* OH* OL* )
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SUB2k NIP2 ( F* U'* B* -done-length* / FN* SZ* OH* OL* )
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ORAk ,¬-end JCN ( F* U'* B* -done-length* / FN* SZ* OH* OL* )
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POP2 POP2r POP2r ( F* U'* B* / FN* SZ* )
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STH2r STH2r ( F* U'* B* SZ* FN* / )
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JMP2r
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¬-end
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STH2r SWP2 ( F* U'* B* OL* -done-length* / FN* SZ* OH* )
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LTH2k JMP INC2r ( F* U'* B* OL* -done-length* / FN* SZ* OH'* )
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SUB2 ( F* U'* B* OL'* / FN* SZ* OH'* )
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STH2r STH2r ( F* U'* B* OL'* OH'* SZ* / FN* )
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,&loop JMP
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@ffwd
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LIT2 &length $2
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LIT2 &offset $2
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&coarse ( length* offset* )
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GTH2k ,&fine JCN
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OVR2 .File/length DEO2
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,&addr LDR2 .File/read DEO2
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OVR2 SUB2
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,&coarse JMP
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&fine ( length* offset* )
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.File/length DEO2 ( length* )
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,&addr LDR2 .File/read DEO2
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.File/length DEO2 ( )
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JMP2r
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&addr $2
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(
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# Arguments
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* func* - address of callback routine
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* udata* - userdata to pass to callback routine
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* buf* - address of first byte of buffer of file's contents
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* size* - size in bytes of buffer
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* filename* - address of filename string (zero-terminated)
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All of the arguments are shorts (suffixed by asterisks *).
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# Callback routine
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If you make use of userdata, the signature of the callback routine is:
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)
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( udata* buf* length* -- udata'* done-up-to* )
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(
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* udata* and buf* are as above.
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* length* is the length of the chunk being worked on, which could be less than
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size* when near the end of the file, and func* is called with zero length* to
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signify end of file.
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* udata'* is the (potentially) modified userdata, to be passed on to the next
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callback routine call and returned by file-read-chunks after the last chunk.
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* done-up-to* is the pointer to the first unprocessed byte in the buffer, or
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buf* + length* if the whole chunk was processed.
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If you don't make use of any userdata, feel free to pretend the signature is:
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)
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( buf* length* -- done-up-to* )
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(
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# Userdata
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The udata* parameter is not processed by file-read-chunks, except to keep the
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one returned from one callback to the next. The meaning of its contents is up
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to you - it could simply be a short integer or a pointer to a region of memory.
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# Operation
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file-read-chunks reads a file into the buffer you provide and calls func* with
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JSR2 with each chunk of data, finishing with an empty chunk at end of file.
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file-read-chunks loops until done-up-to* equals buf*, equivalent to when no
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data is processed by func*. This could be because processing cannot continue
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without a larger buffer, an error is detected in the data and further
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processing is pointless, or because the end-of-file empty chunk leaves the
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callback routine with no other choice.
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# Return values
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Since file-read-chunks's input parameters remain available throughout its
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operation, they are not automatically discarded in case they are useful to the
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caller.
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# Discussion about done-up-to*
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file-read-chunks is extra flexible because it doesn't just give you one chance
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to process each part of the file. Consider a func* routine that splits the
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chunk's contents into words separated by whitespace. If the buffer ends with a
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letter, you can't assume that letter is the end of that word - it's more likely
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to be the in the middle of a word that continues on. If func* returns the
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address of the first letter of the word so far, it will be called again with
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that first letter as the first character of the next chunk's buffer. There's no
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need to remember the earlier part of the word because you get presented with
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the whole lot again to give parsing another try.
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That said, func* must make at least _some_ progress through the chunk: if it
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returns the address at the beginning of the buffer, buf*, file-read-chunks will
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terminate and return to its caller. With our word example, a buffer of ten
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bytes will be unable to make progress with words that are ten or more letters
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long. Depending on your application, either make the buffer big enough so that
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progress should always be possible, or find a way to discern this error
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condition from everything working fine.
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# Discussion about recursion
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Since all of file-read-chunks's data is on the working and return stacks, it
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can be called recursively by code running in the callback routine. For example,
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a code assembler can process the phrase "include library.tal" by calling
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file-read-chunks again with library.tal as the filename. There are a couple of
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caveats:
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* the filename string must not reside inside file-read-chunk's working buffer,
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otherwise it gets overwritten by the file's contents and subsequent chunks
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will fail to be read properly; and
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* if the buffer is shared with the parent file-read-chunk, the callback routine
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should stop further processing and return with done-up-to* straight away,
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since the buffer contents have already been replaced by the child
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file-read-chunk.
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# Resuming / starting operation from an arbitrary offset
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You can call file-read-chunks/resume instead of the main routine if you'd like
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to provide your own offset shorts rather than beginning at the start of the
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file. The effective signature for file-read-chunks/resume is:
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)
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( func* udata* buf* size* filename* offset-ls* offset-hs* -- func* udata'* buf* size* filename* )
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(
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# Example callback routines
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This minimal routine is a no-op that "processes" the entire buffer each time
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and returns a valid done-up-to*:
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@quick-but-useless
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ADD2 JMP2r
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This extremely inefficient callback routine simply prints a single character
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from the buffer and asks for the next one. It operates with a buffer that is
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just one byte long, but for extra inefficiency you can assign a much larger
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buffer and it will ignore everything after the first byte each time. If the
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buffer is zero length it returns done-up-to* == buf* so that file-read-chunks
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returns properly.
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@one-at-a-time
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#0000 NEQ2 JMP JMP2r
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LDAk .Console/write DEO
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INC2 JMP2r
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This more efficient example writes the entire chunk to the console before
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requesting the next one by returning. How short can you make a routine that
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does the same?
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@chunk-at-a-time
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&loop
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ORAk ,¬-eof JCN
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POP2 JMP2r
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¬-eof
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STH2
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LDAk .Console/write DEO
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INC2 STH2r #0001 SUB2
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,&loop JMP
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)
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