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-;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
-;;;
-;;; This file is part of GNU Guix.
-;;;
-;;; GNU Guix is free software; you can redistribute it and/or modify it
-;;; under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation; either version 3 of the License, or (at
-;;; your option) any later version.
-;;;
-;;; GNU Guix is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-;;; GNU General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
-
-(define-module (guix zlib)
- #:use-module (rnrs bytevectors)
- #:use-module (ice-9 binary-ports)
- #:use-module (ice-9 match)
- #:use-module (system foreign)
- #:use-module (guix config)
- #:export (zlib-available?
- make-gzip-input-port
- make-gzip-output-port
- call-with-gzip-input-port
- call-with-gzip-output-port
- %default-buffer-size
- %default-compression-level))
-
-;;; Commentary:
-;;;
-;;; Bindings to the gzip-related part of zlib's API. The main limitation of
-;;; this API is that it requires a file descriptor as the source or sink.
-;;;
-;;; Code:
-
-(define %zlib
- ;; File name of zlib's shared library. When updating via 'guix pull',
- ;; '%libz' might be undefined so protect against it.
- (delay (dynamic-link (if (defined? '%libz)
- %libz
- "libz"))))
-
-(define (zlib-available?)
- "Return true if zlib is available, #f otherwise."
- (false-if-exception (force %zlib)))
-
-(define (zlib-procedure ret name parameters)
- "Return a procedure corresponding to C function NAME in libz, or #f if
-either zlib or the function could not be found."
- (match (false-if-exception (dynamic-func name (force %zlib)))
- ((? pointer? ptr)
- (pointer->procedure ret ptr parameters))
- (#f
- #f)))
-
-(define-wrapped-pointer-type <gzip-file>
- ;; Scheme counterpart of the 'gzFile' opaque type.
- gzip-file?
- pointer->gzip-file
- gzip-file->pointer
- (lambda (obj port)
- (format port "#<gzip-file ~a>"
- (number->string (object-address obj) 16))))
-
-(define gzerror
- (let ((proc (zlib-procedure '* "gzerror" '(* *))))
- (lambda (gzfile)
- (let* ((errnum* (make-bytevector (sizeof int)))
- (ptr (proc (gzip-file->pointer gzfile)
- (bytevector->pointer errnum*))))
- (values (bytevector-sint-ref errnum* 0
- (native-endianness) (sizeof int))
- (pointer->string ptr))))))
-
-(define gzdopen
- (let ((proc (zlib-procedure '* "gzdopen" (list int '*))))
- (lambda (fd mode)
- "Open file descriptor FD as a gzip stream with the given MODE. MODE must
-be a string denoting the how FD is to be opened, such as \"r\" for reading or
-\"w9\" for writing data compressed at level 9 to FD. Calling 'gzclose' also
-closes FD."
- (let ((result (proc fd (string->pointer mode))))
- (if (null-pointer? result)
- (throw 'zlib-error 'gzdopen)
- (pointer->gzip-file result))))))
-
-(define gzread!
- (let ((proc (zlib-procedure int "gzread" (list '* '* unsigned-int))))
- (lambda* (gzfile bv #:optional (start 0) (count (bytevector-length bv)))
- "Read up to COUNT bytes from GZFILE into BV at offset START. Return the
-number of uncompressed bytes actually read; it is zero if COUNT is zero or if
-the end-of-stream has been reached."
- (let ((ret (proc (gzip-file->pointer gzfile)
- (bytevector->pointer bv start)
- count)))
- (if (< ret 0)
- (throw 'zlib-error 'gzread! ret)
- ret)))))
-
-(define gzwrite
- (let ((proc (zlib-procedure int "gzwrite" (list '* '* unsigned-int))))
- (lambda* (gzfile bv #:optional (start 0) (count (bytevector-length bv)))
- "Write up to COUNT bytes from BV at offset START into GZFILE. Return
-the number of uncompressed bytes written, a strictly positive integer."
- (let ((ret (proc (gzip-file->pointer gzfile)
- (bytevector->pointer bv start)
- count)))
- (if (<= ret 0)
- (throw 'zlib-error 'gzwrite ret)
- ret)))))
-
-(define gzbuffer!
- (let ((proc (zlib-procedure int "gzbuffer" (list '* unsigned-int))))
- (lambda (gzfile size)
- "Change the internal buffer size of GZFILE to SIZE bytes."
- (let ((ret (proc (gzip-file->pointer gzfile) size)))
- (unless (zero? ret)
- (throw 'zlib-error 'gzbuffer! ret))))))
-
-(define gzeof?
- (let ((proc (zlib-procedure int "gzeof" '(*))))
- (lambda (gzfile)
- "Return true if the end-of-file has been reached on GZFILE."
- (not (zero? (proc (gzip-file->pointer gzfile)))))))
-
-(define gzclose
- (let ((proc (zlib-procedure int "gzclose" '(*))))
- (lambda (gzfile)
- "Close GZFILE."
- (let ((ret (proc (gzip-file->pointer gzfile))))
- (unless (zero? ret)
- (throw 'zlib-error 'gzclose ret (gzerror gzfile)))))))
-
-
-
-;;;
-;;; Port interface.
-;;;
-
-(define %default-buffer-size
- ;; Default buffer size, as documented in <zlib.h>.
- 8192)
-
-(define %default-compression-level
- ;; Z_DEFAULT_COMPRESSION.
- -1)
-
-(define* (make-gzip-input-port port #:key (buffer-size %default-buffer-size))
- "Return an input port that decompresses data read from PORT, a file port.
-PORT is automatically closed when the resulting port is closed. BUFFER-SIZE
-is the size in bytes of the internal buffer, 8 KiB by default; using a larger
-buffer increases decompression speed. An error is thrown if PORT contains
-buffered input, which would be lost (and is lost anyway)."
- (define gzfile
- (match (drain-input port)
- ("" ;PORT's buffer is empty
- ;; 'gzclose' will eventually close the file descriptor beneath PORT.
- ;; 'close-port' on PORT would get EBADF if 'gzclose' already closed it,
- ;; so that's no good; revealed ports are no good either because they
- ;; leak (see <https://bugs.gnu.org/28784>); calling 'close-port' after
- ;; 'gzclose' doesn't work either because it leads to a race condition
- ;; (see <https://bugs.gnu.org/29335>). So we dup and close PORT right
- ;; away.
- (gzdopen (dup (fileno port)) "r"))
- (_
- ;; This is unrecoverable but it's better than having the buffered input
- ;; be lost, leading to unclear end-of-file or corrupt-data errors down
- ;; the path.
- (throw 'zlib-error 'make-gzip-input-port
- "port contains buffered input" port))))
-
- (define (read! bv start count)
- (gzread! gzfile bv start count))
-
- (unless (= buffer-size %default-buffer-size)
- (gzbuffer! gzfile buffer-size))
-
- (close-port port) ;we no longer need it
- (make-custom-binary-input-port "gzip-input" read! #f #f
- (lambda ()
- (gzclose gzfile))))
-
-(define* (make-gzip-output-port port
- #:key
- (level %default-compression-level)
- (buffer-size %default-buffer-size))
- "Return an output port that compresses data at the given LEVEL, using PORT,
-a file port, as its sink. PORT is automatically closed when the resulting
-port is closed."
- (define gzfile
- (begin
- (force-output port) ;empty PORT's buffer
- (gzdopen (dup (fileno port))
- (string-append "w" (number->string level)))))
-
- (define (write! bv start count)
- (gzwrite gzfile bv start count))
-
- (unless (= buffer-size %default-buffer-size)
- (gzbuffer! gzfile buffer-size))
-
- (close-port port)
- (make-custom-binary-output-port "gzip-output" write! #f #f
- (lambda ()
- (gzclose gzfile))))
-
-(define* (call-with-gzip-input-port port proc
- #:key (buffer-size %default-buffer-size))
- "Call PROC with a port that wraps PORT and decompresses data read from it.
-PORT is closed upon completion. The gzip internal buffer size is set to
-BUFFER-SIZE bytes."
- (let ((gzip (make-gzip-input-port port #:buffer-size buffer-size)))
- (dynamic-wind
- (const #t)
- (lambda ()
- (proc gzip))
- (lambda ()
- (close-port gzip)))))
-
-(define* (call-with-gzip-output-port port proc
- #:key
- (level %default-compression-level)
- (buffer-size %default-buffer-size))
- "Call PROC with an output port that wraps PORT and compresses data. PORT is
-close upon completion. The gzip internal buffer size is set to BUFFER-SIZE
-bytes."
- (let ((gzip (make-gzip-output-port port
- #:level level
- #:buffer-size buffer-size)))
- (dynamic-wind
- (const #t)
- (lambda ()
- (proc gzip))
- (lambda ()
- (close-port gzip)))))
-
-;;; zlib.scm ends here
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