/usr/share/common-lisp/source/chipz/inflate.lisp is in cl-chipz 20130128-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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(defun update-window (state)
(declare (type inflate-state state))
(let* ((output (inflate-state-output state))
(start (inflate-state-output-start state))
(index (inflate-state-output-index state))
(n-bytes-to-copy (- index start))
(window (inflate-state-window state))
(window-index (inflate-state-window-index state)))
(cond
((>= n-bytes-to-copy (length window))
;; can "flush" the window
(setf (inflate-state-window-index state) 0)
(replace window output :start2 (- index (length window))
:end2 index))
(t
(let ((window-space (- (length window) window-index)))
(cond
((> n-bytes-to-copy window-space)
(replace window output :start1 window-index
:start2 start :end2 index)
(replace window output
:start2 (+ start window-space)
:end2 index)
(setf (inflate-state-window-index state)
(- n-bytes-to-copy window-space)))
(t
(replace window output :start1 window-index
:start2 start :end2 index)
(setf (inflate-state-window-index state)
(mod (+ window-index n-bytes-to-copy) (length window))))))))))
;;; This is used behind-the-scenes to do efficient buffer->buffer
;;; decompression. Everything user-visible that's related to
;;; decompression ultimately comes down to this function.
(defun %inflate (state input output &key (input-start 0) input-end
(output-start 0) output-end)
"Decompresses data in INPUT between INPUT-START and INPUT-END
and places the result in OUTPUT between OUTPUT-START and
OUTPUT-END. -START and -END arguments follow the convention of
the sequence functions. Returns the number of bytes pulled from
the input and the number of bytes written to the output."
(declare (type inflate-state state))
(let* ((input-end (or input-end (length input)))
(output-end (or output-end (length output))))
(setf (inflate-state-input state) input
(inflate-state-input-start state) input-start
(inflate-state-input-index state) input-start
(inflate-state-input-end state) input-end
(inflate-state-output state) output
(inflate-state-output-start state) output-start
(inflate-state-output-index state) output-start
(inflate-state-output-end state) output-end)
(catch 'inflate-done
(%inflate-state-machine state))
(update-window state)
(when (dstate-update-checksum state)
(funcall (dstate-update-checksum state)
(dstate-checksum state) output output-start
(inflate-state-output-index state)))
(values (- (inflate-state-input-index state) input-start)
(- (inflate-state-output-index state) output-start))))
(defun record-code-length (state value)
(setf (aref (inflate-state-code-lengths state)
(aref *code-length-code-order*
(inflate-state-n-values-read state))) value)
(incf (inflate-state-n-values-read state)))
;;; internal inflate function
(defun %inflate-state-machine (state)
(declare (type inflate-state state))
(declare (optimize (speed 3) (debug 1) (space 0) (compilation-speed 0)))
;; Once upon a time, the individual functions in the LABELS below were
;; separate functions. We drove the state machine of this function
;; using LOOP and SYMBOL-FUNCTION. This scheme looked lovely...except
;; that SYMBOL-FUNCTION is a horrible thing to call in inner loops,
;; and we were calling it for just about every byte of input.
;;
;; So we switched to this huge LABELS. Each function then stored a
;; reference to its next state in INFLATE-STATE-STATE before jumping
;; to the next function. Some compilers were even able to optimize
;; the call into a fallthru, which provides a nice approximation of a
;; C switch statement. That was fine and dandy...except that the jump
;; is a tail call, Common Lisp is not Scheme, and some implementations
;; do not optimize tail calls. This combination led to stack
;; overflows if you handed a large input buffer to this function.
;;
;; So we provide alternatives now through the TRANSITION-TO macro. On
;; implementations we're sure we can trust to DTRT, we keep the second
;; scheme above. On other implementations, we use a variant of the
;; first scheme we tried, which is to simply store the next state's
;; function in INFLATE-STATE-STATE and return. This at least avoids
;; SYMBOL-FUNCTION and keeps constant stack space; the LOOP in the
;; body of the LABELS (waaay down there) makes sure that we don't stop
;; until we THROW.
(macrolet ((transition-to (next-state)
`(progn
(setf (inflate-state-state state) #',next-state)
#+(or sbcl cmu)
(,next-state state)
;; Just fall through for other implementations and
;; return normally.
)))
(labels (
(read-bits (n state)
(declare (type (integer 0 32) n))
(declare (type inflate-state state))
(prog1 (ldb (byte n 0) (inflate-state-bits state))
(setf (inflate-state-bits state)
(ash (inflate-state-bits state) (- n)))
(decf (inflate-state-n-bits state) n)))
(ensure-bits (n state)
(declare (type (integer 0 32) n))
(declare (type inflate-state state))
(let ((bits (inflate-state-bits state))
(n-bits (inflate-state-n-bits state))
(input-index (inflate-state-input-index state)))
(declare (type (unsigned-byte 32) bits))
(loop while (< n-bits n)
when (>= input-index (inflate-state-input-end state))
do (progn
(setf (inflate-state-bits state) bits
(inflate-state-n-bits state) n-bits
(inflate-state-input-index state) input-index)
(throw 'inflate-done nil))
do (let ((byte (aref (inflate-state-input state) input-index)))
(declare (type (unsigned-byte 8) byte))
(setf bits
(logand #xffffffff (logior (ash byte n-bits) bits)))
(incf n-bits 8)
(incf input-index))
finally (setf (inflate-state-bits state) bits
(inflate-state-n-bits state) n-bits
(inflate-state-input-index state) input-index))))
(ensure-and-read-bits (n state)
(ensure-bits n state)
(read-bits n state))
(align-bits-bytewise (state)
(declare (type inflate-state state))
(let ((n-bits (inflate-state-n-bits state)))
(decf (inflate-state-n-bits state) (rem n-bits 8))
(setf (inflate-state-bits state)
(ash (inflate-state-bits state)
(- (rem n-bits 8))))
(values)))
(decode-value (table state)
(declare (type huffman-decode-table table))
(declare (type inflate-state state))
(declare (optimize (speed 3)))
(ensure-bits (hdt-bits table) state)
(let ((bits (inflate-state-bits state)))
(declare (type (unsigned-byte 32) bits))
(do ((counts (hdt-counts table))
(len 1 (1+ len))
(first 0 (probably-the-fixnum (ash first 1)))
(code 0 (probably-the-fixnum (ash code 1))))
((>= len +max-code-length+) nil)
(declare (type (and fixnum (integer 0 *)) first code))
;; We would normally do this with READ-BITS, but DECODE-VALUE
;; is a hotspot in profiles along with this would-be call to
;; READ-BITS, so we inline it all here.
(setf code (logior code (logand bits 1))
bits (ash bits -1))
(let ((count (aref counts len)))
(when (< (- code count) first)
(setf (inflate-state-bits state) bits)
(decf (inflate-state-n-bits state) len)
(return-from decode-value (aref (hdt-symbols table)
(probably-the-fixnum
(+ (aref (hdt-offsets table) (1- len))
(- code first))))))
(setf first
(probably-the-fixnum (+ first count)))))))
(read-dynamic-table (state decoder n-values)
(declare (type inflate-state state))
(loop with lengths = (inflate-state-code-lengths state)
while (< (inflate-state-n-values-read state) n-values)
do (ensure-bits (+ (hdt-bits decoder) 7) state)
(let ((value (decode-value decoder state)))
(cond
((< value 16)
(setf (aref lengths (inflate-state-n-values-read state)) value)
(incf (inflate-state-n-values-read state)))
(t
(let ((len 0) (sym 0))
(cond
((= value 16)
(setf sym (aref lengths (1- (inflate-state-n-values-read state))))
(setf len (+ 3 (read-bits 2 state))))
((= value 17)
(setf len (+ 3 (read-bits 3 state))))
((= value 18)
(setf len (+ 11 (read-bits 7 state)))))
(fill lengths sym :start (inflate-state-n-values-read state)
:end (+ (inflate-state-n-values-read state) len))
(incf (inflate-state-n-values-read state) len)))))
finally (progn
(assert (= n-values (inflate-state-n-values-read state)))
(return (construct-huffman-decode-table lengths n-values)))))
;; Basic starter functions.
(done (state)
(declare (ignore state))
(throw 'inflate-done t))
(block-type (state)
(cond
((inflate-state-final-block-p state)
(align-bits-bytewise state)
(setf (inflate-state-state state)
(ecase (inflate-state-data-format state)
(deflate
(setf (inflate-state-done state) t)
#'done)
(zlib #'check-zlib-adler32)
(gzip #'gzip-crc32))))
(t
(ensure-bits 3 state)
(setf (inflate-state-final-block-p state) (= 1 (read-bits 1 state)))
(ecase (read-bits 2 state)
(#.+block-no-compress+
(transition-to uncompressed-block))
(#.+block-fixed-codes+
(setf (inflate-state-literal/length-table state)
*fixed-literal/length-table*
(inflate-state-distance-table state)
*fixed-distance-table*)
(transition-to literal/length))
(#.+block-dynamic-codes+
(transition-to dynamic-tables))
(#.+block-invalid+
(error 'reserved-block-type-error))))))
;;; processing uncompressed blocks
(uncompressed-block (state)
(align-bits-bytewise state)
(let* ((len (ensure-and-read-bits 16 state))
(nlen (ensure-and-read-bits 16 state)))
(unless (zerop (logand len nlen))
;; Apparently Adobe's PDF generator(s) get this wrong, so let the
;; user continue on if they choose to do so.
(cerror "Use the invalid stored block length."
'invalid-stored-block-length-error))
(setf (inflate-state-length state) len)
(transition-to copy-bytes)))
(copy-bytes (state)
(declare (type inflate-state state))
(if (zerop (inflate-state-length state))
(setf (inflate-state-state state) #'block-type)
(let ((n-copied-bytes (min (inflate-state-length state)
(- (inflate-state-input-end state)
(inflate-state-input-index state))
(- (inflate-state-output-end state)
(inflate-state-output-index state)))))
(cond
((zerop n-copied-bytes) (throw 'inflate-done nil))
(t
(replace (inflate-state-output state)
(inflate-state-input state)
:start1 (inflate-state-output-index state)
:end1 (+ (inflate-state-output-index state)
n-copied-bytes)
:start2 (inflate-state-input-index state)
:end2 (+ (inflate-state-input-index state)
n-copied-bytes))
(incf (inflate-state-input-index state) n-copied-bytes)
(incf (inflate-state-output-index state) n-copied-bytes)
(decf (inflate-state-length state) n-copied-bytes)))))
(values))
;;; dynamic block compression tables
(dynamic-tables (state)
(declare (type inflate-state state))
(ensure-bits 14 state)
(setf (inflate-state-n-length-codes state) (+ (read-bits 5 state) 257)
(inflate-state-n-distance-codes state) (+ (read-bits 5 state) 1)
(inflate-state-n-codes state) (+ (read-bits 4 state) 4)
(inflate-state-n-values-read state) 0)
(transition-to dynamic-code-lengths))
(dynamic-code-lengths (state)
(declare (type inflate-state state))
(loop while (< (inflate-state-n-values-read state)
(inflate-state-n-codes state))
do (ensure-bits 3 state)
(record-code-length state (read-bits 3 state)))
(loop while (< (inflate-state-n-values-read state) +max-n-code-lengths+)
do (record-code-length state 0))
(setf (inflate-state-codes-table state)
(construct-huffman-decode-table (inflate-state-code-lengths state)
+max-n-code-lengths+)
(inflate-state-n-values-read state) 0)
(transition-to dynamic-literal/length-table))
(dynamic-literal/length-table (state)
(declare (type inflate-state state))
(setf (inflate-state-literal/length-table state)
(read-dynamic-table state (inflate-state-codes-table state)
(inflate-state-n-length-codes state))
(inflate-state-n-values-read state) 0)
(transition-to dynamic-distance-table))
(dynamic-distance-table (state)
(declare (type inflate-state state))
(setf (inflate-state-distance-table state)
(read-dynamic-table state (inflate-state-codes-table state)
(inflate-state-n-distance-codes state)))
(transition-to literal/length))
;;; normal operation on compressed blocks
(literal/length (state)
(declare (type inflate-state state))
(let ((value (decode-value (inflate-state-literal/length-table state)
state)))
(declare (type (integer 0 288) value))
(cond
((< value 256)
(setf (inflate-state-length state) value)
(transition-to literal))
((> value 256)
(setf (inflate-state-length-code state) (- value 257))
(transition-to length-code))
(t #+nil (= value 256)
(transition-to block-type)))))
(literal (state)
(declare (type inflate-state state))
(cond
((= (inflate-state-output-index state)
(inflate-state-output-end state)) (throw 'inflate-done nil))
(t (setf (aref (inflate-state-output state)
(inflate-state-output-index state))
(inflate-state-length state))
(incf (inflate-state-output-index state))
(transition-to literal/length))))
(length-code (state)
(declare (type inflate-state state))
(let* ((length-code (inflate-state-length-code state))
(length-extra (ensure-and-read-bits (n-length-extra-bits length-code) state)))
(setf (inflate-state-length state)
(+ (length-base length-code) length-extra))
(transition-to distance)))
(distance (state)
(declare (type inflate-state state))
(let ((value (decode-value (inflate-state-distance-table state)
state)))
(setf (inflate-state-distance state) value)
(transition-to distance-extra)))
(distance-extra (state)
(declare (type inflate-state state))
(let* ((bits (n-distance-extra-bits (inflate-state-distance state)))
(distance-extra (if (zerop bits)
0
(ensure-and-read-bits bits state))))
(setf (inflate-state-distance state)
(+ (distance-base (inflate-state-distance state)) distance-extra))
(transition-to copy-match)))
(copy-match (state)
(declare (type inflate-state state))
(let* ((distance (inflate-state-distance state))
(length (inflate-state-length state))
(start (inflate-state-output-start state))
(index (inflate-state-output-index state))
(end (inflate-state-output-end state))
(window-index (inflate-state-window-index state))
(n-bytes-to-copy (min length (- end index))))
(when (= index end)
(throw 'inflate-done nil))
(flet ((frob-by-copying-from (copy-source copy-index n-bytes-to-copy)
(declare (type (simple-array (unsigned-byte 8) (*)) copy-source))
(decf (inflate-state-length state) n-bytes-to-copy)
(incf (inflate-state-output-index state) n-bytes-to-copy)
(loop with output = (inflate-state-output state)
for i from index below (the fixnum (+ index n-bytes-to-copy))
for j from copy-index below (the fixnum (+ copy-index n-bytes-to-copy))
do (setf (aref output i) (aref copy-source j)))))
(cond
((<= distance (- index start))
;; we are within the output we have produced
(frob-by-copying-from (inflate-state-output state)
(- index distance)
n-bytes-to-copy))
(t
(let ((copy-index (+ (- window-index distance) (- index start))))
(cond
((not (minusp copy-index))
;; we are within the non-wraparound portion of the window
;;
;; can only copy up to the window's index, though
(let ((n-bytes-to-copy (min n-bytes-to-copy (- window-index copy-index))))
(frob-by-copying-from (inflate-state-window state)
copy-index
n-bytes-to-copy)))
(t
;; we are within the wraparound portion of the window
(let* ((copy-index (+ copy-index
(length (inflate-state-window state))))
(n-bytes-to-copy (min n-bytes-to-copy
(- (length (inflate-state-window state))
copy-index))))
(frob-by-copying-from (inflate-state-window state)
copy-index
n-bytes-to-copy)))))))
(when (zerop (inflate-state-length state))
(transition-to literal/length)))))
;; GZIP
(gzip-header-id (state)
(declare (type inflate-state state))
(let ((header-field (ensure-and-read-bits 16 state)))
(unless (and (= (ldb (byte 8 0) header-field) #x1f)
(= (ldb (byte 8 8) header-field) #x8b))
(error 'invalid-gzip-header-error))
(transition-to gzip-cm)))
(gzip-cm (state)
(declare (type inflate-state state))
(let ((cm-byte (ensure-and-read-bits 8 state)))
(setf (inflate-state-header state)
(make-instance 'gzip-header :compression-method cm-byte))
(transition-to gzip-flags)))
(gzip-flags (state)
(declare (type inflate-state state))
(let ((flags-byte (ensure-and-read-bits 8 state)))
(setf (flags (inflate-state-header state)) flags-byte)
(transition-to gzip-mtime)))
(gzip-mtime (state)
(declare (type inflate-state state))
(let ((mtime (ensure-and-read-bits 32 state)))
(setf (mtime (inflate-state-header state)) mtime)
(transition-to gzip-xfl)))
(gzip-xfl (state)
(declare (type inflate-state state))
(let ((xfl-byte (ensure-and-read-bits 8 state)))
(setf (extra-flags (inflate-state-header state)) xfl-byte)
(transition-to gzip-os)))
(gzip-os (state)
(declare (type inflate-state state))
(let ((os-byte (ensure-and-read-bits 8 state)))
(setf (os (inflate-state-header state)) os-byte)
(transition-to gzip-xlen-len)))
(gzip-xlen-len (state)
(declare (type inflate-state state))
(let ((flags (flags (inflate-state-header state))))
(cond
((logbitp +gzip-flag-extra+ flags)
(error "gzip extra field not supported yet"))
(t
(transition-to gzip-fname)))))
(gzip-fname (state)
(declare (type inflate-state state))
(process-gzip-zero-terminated-field state +gzip-flag-name+
#'filename #'(setf filename)
#'gzip-fcomment))
(gzip-fcomment (state)
(declare (type inflate-state state))
(process-gzip-zero-terminated-field state +gzip-flag-comment+
#'comment #'(setf comment)
#'gzip-crc16))
(process-gzip-zero-terminated-field (state control-bit
slot set-slot
next-state)
(let ((header (inflate-state-header state)))
(cond
((logbitp control-bit (flags header))
(let ((byte (ensure-and-read-bits 8 state)))
(cond
((zerop byte)
;; the end, convert to sane form
(funcall set-slot
(coerce (funcall slot header)
'(vector (unsigned-byte 8)))
header)
(setf (inflate-state-state state) next-state))
(t
;; wish we could use PUSH here
(funcall set-slot
(cons byte (funcall slot header))
header)))))
(t
(setf (inflate-state-state state) next-state)))
(values)))
(gzip-crc16 (state)
(declare (type inflate-state state))
(let ((header (inflate-state-header state)))
(when (logbitp +gzip-flag-crc+ (flags header))
(let ((crc16 (ensure-and-read-bits 16 state)))
;; FIXME: would be good to perform integrity checking here
(declare (ignore crc16))))
(transition-to block-type)))
(gzip-crc32 (state)
(declare (type inflate-state state))
(let ((stored (ensure-and-read-bits 32 state))
(crc32 (copy-crc32 (inflate-state-checksum state))))
(update-crc32 crc32
(inflate-state-output state)
(inflate-state-output-start state)
(inflate-state-output-index state))
(unless (= stored (produce-crc32 crc32))
(error 'invalid-checksum-error
:stored stored
:computed (produce-crc32 crc32)
:kind :crc32))
(transition-to gzip-isize)))
(gzip-isize (state)
(declare (type inflate-state state))
(let ((isize (ensure-and-read-bits 32 state)))
(declare (ignore isize))
(setf (inflate-state-done state) t)
(transition-to done)))
;; ZLIB
(zlib-cmf (state)
(declare (type inflate-state state))
(let ((cmf-byte (ensure-and-read-bits 8 state)))
(setf (inflate-state-header state)
(make-instance 'zlib-header :cmf cmf-byte))
(transition-to zlib-flags)))
(zlib-flags (state)
(declare (type inflate-state state))
(let ((flags-byte (ensure-and-read-bits 8 state))
(header (inflate-state-header state)))
;; check
(unless (zerop (mod (+ (* (cmf header) 256) flags-byte) 31))
(error 'invalid-zlib-header-error))
(setf (flags header) flags-byte)
(transition-to zlib-fdict)))
(zlib-fdict (state)
(declare (type inflate-state state))
(let* ((header (inflate-state-header state))
(flags-byte (flags header)))
(when (logbitp +zlib-flag-fdict+ flags-byte)
(let ((fdict (ensure-and-read-bits 32 state)))
(setf (fdict header) fdict)))
(transition-to block-type)))
(check-zlib-adler32 (state)
(declare (type inflate-state state))
(let ((stored (let ((x (ensure-and-read-bits 32 state)))
(logior (ash (ldb (byte 8 0) x) 24)
(ash (ldb (byte 8 8) x) 16)
(ash (ldb (byte 8 16) x) 8)
(ldb (byte 8 24) x))))
(adler32 (copy-adler32 (inflate-state-checksum state))))
(update-adler32 adler32
(inflate-state-output state)
(inflate-state-output-start state)
(inflate-state-output-index state))
(unless (= stored
(produce-adler32 adler32))
(error 'invalid-checksum-error
:stored stored
:computed (produce-adler32 adler32)
:kind :adler32))
(setf (inflate-state-done state) t)
(transition-to done)))
)
(unless (inflate-state-state state)
(setf (inflate-state-state state)
(ecase (inflate-state-data-format state)
(deflate #'block-type)
(zlib #'zlib-cmf)
(gzip #'gzip-header-id))))
(loop (funcall (inflate-state-state state) state)))))
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