/* iobuf.h - I/O buffer

 * Copyright (C) 1998, 1999, 2000, 2001, 2003,

 *               2010 Free Software Foundation, Inc.

 *

 * This file is part of GnuPG.

 *

 * This file is free software; you can redistribute it and/or modify

 * it under the terms of either

 *

 *   - the GNU Lesser General Public License as published by the Free

 *     Software Foundation; either version 3 of the License, or (at

 *     your option) any later version.

 *

 * or

 *

 *   - the GNU General Public License as published by the Free

 *     Software Foundation; either version 2 of the License, or (at

 *     your option) any later version.

 *

 * or both in parallel, as here.

 *

 * This file 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 this program; if not, see <https://www.gnu.org/licenses/>.

 */

#ifndef GNUPG_COMMON_IOBUF_H

#define GNUPG_COMMON_IOBUF_H

/* An iobuf is basically a filter in a pipeline.

   Consider the following command, which consists of three filters

   that are chained together:

     $ cat file | base64 --decode | gunzip

   The first filter reads the file from the file system and sends that

   data to the second filter.  The second filter decodes

   base64-encoded data and sends the data to the third and last

   filter.  The last filter decompresses the data and the result is

   displayed on the terminal.  The iobuf system works in the same way

   where each iobuf is a filter and the individual iobufs can be

   chained together.

   There are number of predefined filters.  iobuf_open(), for

   instance, creates a filter that reads from a specified file.  And,

   iobuf_temp_with_content() creates a filter that returns some

   specified contents.  There are also filters for writing content.

   iobuf_openrw opens a file for writing.  iobuf_temp creates a filter

   that writes data to a fixed-sized buffer.

   To chain filters together, you use the iobuf_push_filter()

   function.  The filters are chained together using the chain field

   in the iobuf_t.

   A pipeline can only be used for reading (IOBUF_INPUT) or for

   writing (IOBUF_OUTPUT / IOBUF_OUTPUT_TEMP).  When reading, data

   flows from the last filter towards the first.  That is, the user

   calls iobuf_read(), the module reads from the first filter, which

   gets its input from the second filter, etc.  When writing, data

   flows from the first filter towards the last.  In this case, when

   the user calls iobuf_write(), the data is written to the first

   filter, which writes the transformed data to the second filter,

   etc.

   An iobuf_t contains some state about the filter.  For instance, it

   indicates if the filter has already returned EOF (filter_eof) and

   the next filter in the pipeline, if any (chain).  It also contains

   a function pointer, filter.  This is a generic function.  It is

   called when input is needed or output is available.  In this case

   it is passed a pointer to some filter-specific persistent state

   (filter_ov), the actual operation, the next filter in the chain, if

   any, and a buffer that either contains the contents to write, if

   the pipeline is setup to write data, or is the place to store data,

   if the pipeline is setup to read data.

   Unlike a Unix pipeline, an IOBUF pipeline can return EOF multiple

   times.  This is similar to the following:

     { cat file1; cat file2; } | grep foo

   However, instead of grep seeing a single stream, grep would see

   each byte stream followed by an EOF marker.  (When a filter returns

   EOF, the EOF is returned to the user exactly once and then the

   filter is removed from the pipeline.)  */

/* For estream_t.  */

#include <gpg-error.h>

#include "../common/types.h"

#include "../common/sysutils.h"

#define DBG_IOBUF   iobuf_debug_mode

/* Filter control modes.  */

enum

  {

    IOBUFCTRL_INIT  = 1,

    IOBUFCTRL_FREE  = 2,

    IOBUFCTRL_UNDERFLOW = 3,

    IOBUFCTRL_FLUSH     = 4,

    IOBUFCTRL_DESC  = 5,

    IOBUFCTRL_CANCEL    = 6,

    IOBUFCTRL_PEEK      = 7,

    IOBUFCTRL_USER  = 16

  };

/* Command codes for iobuf_ioctl.  */

typedef enum

  {

    IOBUF_IOCTL_KEEP_OPEN        = 1, /* Uses intval.  */

    IOBUF_IOCTL_INVALIDATE_CACHE = 2, /* Uses ptrval.  */

    IOBUF_IOCTL_NO_CACHE         = 3, /* Uses intval.  */

    IOBUF_IOCTL_FSYNC            = 4, /* Uses ptrval.  */

    IOBUF_IOCTL_PEEK             = 5  /* Uses intval and ptrval.  */

  } iobuf_ioctl_t;

enum iobuf_use

  {

    /* Pipeline is in input mode.  The data flows from the end to the

       beginning.  That is, when reading from the pipeline, the first

       filter gets its input from the second filter, etc.  */

    IOBUF_INPUT,

    /* Pipeline is in input mode.  The last filter in the pipeline is

       a temporary buffer from which the data is "read".  */

    IOBUF_INPUT_TEMP,

    /* Pipeline is in output mode.  The data flows from the beginning

       to the end.  That is, when writing to the pipeline, the user

       writes to the first filter, which transforms the data and sends

       it to the second filter, etc.  */

    IOBUF_OUTPUT,

    /* Pipeline is in output mode.  The last filter in the pipeline is

       a temporary buffer that grows as necessary.  */

    IOBUF_OUTPUT_TEMP

  };

typedef struct iobuf_struct *iobuf_t;

typedef struct iobuf_struct *IOBUF;  /* Compatibility with gpg 1.4. */

/* fixme: we should hide most of this stuff */

struct iobuf_struct

{

  /* The type of filter.  Either IOBUF_INPUT, IOBUF_OUTPUT or

     IOBUF_OUTPUT_TEMP.  */

  enum iobuf_use use;

  /* nlimit can be changed using iobuf_set_limit.  If non-zero, it is

     the number of additional bytes that can be read from the filter

     before EOF is forcefully returned.  */

  off_t nlimit;

  /* nbytes if the number of bytes that have been read (using

     iobuf_get / iobuf_readbyte / iobuf_read) since the last call to

     iobuf_set_limit.  */

  off_t nbytes;

  /* The number of bytes read prior to the last call to

     iobuf_set_limit.  Thus, the total bytes read (i.e., the position

     of stream) is ntotal + nbytes. */

  off_t ntotal;

  /* Whether we need to read from the filter one byte at a time or

     whether we can do bulk reads.  We need to read one byte at a time

     if a limit (set via iobuf_set_limit) is active.  */

  int nofast;

  /* A buffer for unread/unwritten data.

     For an output pipeline (IOBUF_OUTPUT), this is the data that has

     not yet been written to the filter.  Consider a simple pipeline

     consisting of a single stage, which writes to a file.  When you

     write to the pipeline (iobuf_writebyte or iobuf_write), the data

     is first stored in this buffer.  Only when the buffer is full or

     you call iobuf_flush() is FILTER actually called and the data

     written to the file.

     For an input pipeline (IOBUF_INPUT), this is the data that has

     been read from this filter, but not yet been read from the

     preceding filter (or the user, if this filter is the head of the

     pipeline).  Again, consider a simple pipeline consisting of a

     single stage.  This stage reads from a file.  If you read a

     single byte (iobuf_get) and the buffer is empty, then FILTER is

     called to fill the buffer.  In this case, a single byte is not

     requested, but the whole buffer is filled (if possible).  */

  struct

  {

    /* Size of the buffer.  */

    size_t size;

    /* Number of bytes at the beginning of the buffer that have

       already been consumed.  (In other words: the index of the first

       byte that hasn't been consumed.)  This is only non-zero for

       input filters.  */

    size_t start;

    /* The number of bytes in the buffer including any bytes that have

       been consumed.  */

    size_t len;

    /* The buffer itself.  */

    byte *buf;

  } d;

  /* A external drain buffer for reading/writing data skipping internal

     draint buffer D.BUF.  This allows zerocopy operation reducing

     processing overhead across filter stack.

     Used when by iobuf_read/iobuf_write when internal buffer has been

     depleted and remaining external buffer length is large enough.

   */

  struct

  {

    /* The external buffer provided by iobuf_read/iobuf_write caller. */

    byte *buf;

    /* The number of bytes in the external buffer. */

    size_t len;

    /* The number of bytes that were consumed from the external buffer. */

    size_t used;

    /* Gives hint for processing that the external buffer is preferred and

       that internal buffer should be consumed early. */

    int preferred;

  } e_d;

  /* When FILTER is called to read some data, it may read some data

     and then return EOF.  We can't return the EOF immediately.

     Instead, we note that we observed the EOF and when the buffer is

     finally empty, we return the EOF.  */

  int filter_eof;

  /* Like filter_eof, when FILTER is called to read some data, it may

     read some data and then return an error.  We can't return the

     error (in the form of an EOF) immediately.  Instead, we note that

     we observed the error and when the buffer is finally empty, we

     return the EOF.  */

  int error;

  /* The callback function to read data from the filter, etc.  See

     iobuf_filter_push for details.  */

  int (*filter) (void *opaque, int control,

     iobuf_t chain, byte * buf, size_t * len);

  /* An opaque pointer that can be used for local filter state.  This

     is passed as the first parameter to FILTER.  */

  void *filter_ov;

  /* Whether the iobuf code should free(filter_ov) when destroying the

     filter.  */

  int filter_ov_owner;

  /* When using iobuf_open, iobuf_create, iobuf_openrw to open a file,

     the file's name is saved here.  This is used to delete the file

     when an output pipeline (IOBUF_OUPUT) is canceled

     (iobuf_cancel).  */

  char *real_fname;

  /* The next filter in the pipeline.  */

  iobuf_t chain;

  /* This field is for debugging.  Each time a filter is allocated

     (via iobuf_alloc()), a monotonically increasing counter is

     incremented and this field is set to the new value.  This field

     should only be accessed via the iobuf_io macro.  */

  int no;

  /* The number of filters in the pipeline following (not including)

     this one.  When you call iobuf_push_filter or iobuf_push_filter2,

     this value is used to check the length of the pipeline if the

     pipeline already contains 65 stages then these functions fail.

     This amount of nesting typically indicates corrupted data or an

     active denial of service attack.  */

  int subno;

};

extern int iobuf_debug_mode;

/* Change the default size for all IOBUFs to KILOBYTE.  This needs to

 * be called before any iobufs are used and can only be used once.

 * Returns the current value.  Using 0 has no effect except for

 * returning the current value.  */

unsigned int iobuf_set_buffer_size (unsigned int kilobyte);

/* Returns whether the specified filename corresponds to a pipe.  In

   particular, this function checks if FNAME is "-" and, if special

   filenames are enabled (see check_special_filename), whether

   FNAME is a special filename.  */

int  iobuf_is_pipe_filename (const char *fname);

/* Allocate a new filter.  This filter doesn't have a function

   assigned to it.  Thus you need to manually set IOBUF->FILTER and

   IOBUF->FILTER_OV, if required.  This function is intended to help

   create a new primary source or primary sink, i.e., the last filter

   in the pipeline.

   USE is IOBUF_INPUT, IOBUF_INPUT_TEMP, IOBUF_OUTPUT or

   IOBUF_OUTPUT_TEMP.

   BUFSIZE is the desired internal buffer size (that is, the size of

   the typical read / write request).  */

iobuf_t iobuf_alloc (int use, size_t bufsize);

/* Create an output filter that simply buffers data written to it.

   This is useful for collecting data for later processing.  The

   buffer can be written to in the usual way (iobuf_write, etc.).  The

   data can later be extracted using iobuf_write_temp() or

   iobuf_temp_to_buffer().  */

iobuf_t iobuf_temp (void);

/* Create an input filter that contains some data for reading.  */

iobuf_t iobuf_temp_with_content (const char *buffer, size_t length);

/* Create an input file filter that reads from a file.  If FNAME is

   '-', reads from stdin.  If special filenames are enabled

   (iobuf_enable_special_filenames), then interprets special

   filenames.  */

iobuf_t iobuf_open (const char *fname);

/* Create an output file filter that writes to a file.  If FNAME is

   NULL or '-', writes to stdout.  If special filenames are enabled

   (iobuf_enable_special_filenames), then interprets special

   filenames.  If FNAME is not NULL, '-' or a special filename, the

   file is opened for writing.  If the file exists, it is truncated.

   If MODE700 is TRUE, the file is created with mode 600.  Otherwise,

   mode 666 is used.  */

iobuf_t iobuf_create (const char *fname, int mode700);

/* Create an output file filter that writes to a specified file.

   Neither '-' nor special file names are recognized.  */

iobuf_t iobuf_openrw (const char *fname);

/* Create a file filter using an existing file descriptor.  If MODE

   contains the letter 'w', creates an output filter.  Otherwise,

   creates an input filter.  Note: MODE must reflect the file

   descriptors actual mode!  When the filter is destroyed, the file

   descriptor is closed.  */

iobuf_t iobuf_fdopen (gnupg_fd_t fd, const char *mode);

/* Like iobuf_fdopen, but doesn't close the file descriptor when the

   filter is destroyed.  */

iobuf_t iobuf_fdopen_nc (gnupg_fd_t fd, const char *mode);

/* Create a filter using an existing estream.  If MODE contains the

   letter 'w', creates an output filter.  Otherwise, creates an input

   filter.  If KEEP_OPEN is TRUE, then the stream is not closed when

   the filter is destroyed.  Otherwise, the stream is closed when the

   filter is destroyed.  If READLIMIT is not 0 this gives a limit on

   the number of bytes to read from estream.  */

iobuf_t iobuf_esopen (estream_t estream, const char *mode, int keep_open,

                      size_t readlimit);

/* Create a filter using an existing socket.  On Windows creates a

   special socket filter.  On non-Windows systems simply, this simply

   calls iobuf_fdopen.  */

iobuf_t iobuf_sockopen (int fd, const char *mode);

/* Set various options / perform different actions on a PIPELINE.  See

   the IOBUF_IOCTL_* macros above.  */

int iobuf_ioctl (iobuf_t a, iobuf_ioctl_t cmd, int intval, void *ptrval);

/* Close a pipeline.  The filters in the pipeline are first flushed

   using iobuf_flush, if they are output filters, and then

   IOBUFCTRL_FREE is called on each filter.

   If any filter returns a non-zero value in response to the

   IOBUFCTRL_FREE, that first such non-zero value is returned.  Note:

   processing is not aborted in this case.  If all filters are freed

   successfully, 0 is returned.  */

int iobuf_close (iobuf_t iobuf);

/* Calls IOBUFCTRL_CANCEL on each filter in the pipeline.  Then calls

   io_close() on the pipeline.  Finally, if the pipeline is an output

   pipeline, deletes the file.  Returns the result of calling

   iobuf_close on the pipeline.  */

int iobuf_cancel (iobuf_t iobuf);

/* Add a new filter to the front of a pipeline.  A is the head of the

   pipeline.  F is the filter implementation.  OV is an opaque pointer

   that is passed to F and is normally used to hold any internal

   state, such as a file pointer.

   Note: you may only maintain a reference to an iobuf_t as a

   reference to the head of the pipeline.  That is, don't think about

   setting a pointer in OV to point to the filter's iobuf_t.  This is

   because when we add a new filter to a pipeline, we memcpy the state

   in A into new buffer.  This has the advantage that there is no need

   to update any references to the pipeline when a filter is added or

   removed, but it also means that a filter's state moves around in

   memory.

   The behavior of the filter function is determined by the value of

   the control parameter:

     IOBUFCTRL_INIT: Called this value just before the filter is

       linked into the pipeline. This can be used to initialize

       internal data structures.

     IOBUFCTRL_FREE: Called with this value just before the filter is

       removed from the pipeline.  Normally used to release internal

       data structures, close a file handle, etc.

     IOBUFCTRL_UNDERFLOW: Called with this value to fill the passed

       buffer with more data. *LEN is the size of the buffer.  Before

       returning, it should be set to the number of bytes which were

       written into the buffer.  The function must return 0 to

       indicate success, -1 on EOF and a GPG_ERR_xxxxx code for any

       error.

       Note: this function may both return data and indicate an error

       or EOF.  In this case, it simply writes the data to BUF, sets

       *LEN and returns the appropriate return code.  The implication

       is that if an error occurs and no data has yet been written, it

       is essential that *LEN be set to 0!

     IOBUFCTRL_FLUSH: Called with this value to write out any

       collected data.  *LEN is the number of bytes in BUF that need

       to be written out.  Returns 0 on success and a GPG_ERR_* code

       otherwise.  *LEN must be set to the number of bytes that were

       written out.

     IOBUFCTRL_CANCEL: Called with this value when iobuf_cancel() is

       called on the pipeline.

     IOBUFCTRL_DESC: Called with this value to get a human-readable

       description of the filter.  *LEN is the size of the buffer.

       The description is filled into BUF, NUL-terminated.  Always

       returns 0.

  */

int iobuf_push_filter (iobuf_t a, int (*f) (void *opaque, int control,

              iobuf_t chain, byte * buf,

              size_t * len), void *ov);

/* This variant of iobuf_push_filter allows the called to indicate

   that OV should be freed when this filter is freed.  That is, if

   REL_OV is TRUE, then when the filter is popped or freed OV will be

   freed after the filter function is called with control set to

   IOBUFCTRL_FREE.  */

int iobuf_push_filter2 (iobuf_t a,

      int (*f) (void *opaque, int control, iobuf_t chain,

          byte * buf, size_t * len), void *ov,

      int rel_ov);

/* Pop the top filter.  The top filter must have the filter function F

   and the cookie OV.  The cookie check is ignored if OV is NULL.  */

int iobuf_pop_filter (iobuf_t a,

                      int (*f) (void *opaque, int control,

                                iobuf_t chain, byte * buf, size_t * len),

                      void *ov);

/* Used for debugging.  Prints out the chain using log_debug if

   IOBUF_DEBUG_MODE is not 0.  */

int iobuf_print_chain (iobuf_t a);

/* Indicate that some error occurred on the specified filter.  */

#define iobuf_set_error(a)    do { (a)->error = 1; } while(0)

/* Return any pending error on filter A.  */

#define iobuf_error(a)        ((a)->error)

/* Limit the amount of additional data that may be read from the

   filter.  That is, if you've already read 100 bytes from A and you

   set the limit to 50, then you can read up to an additional 50 bytes

   (i.e., a total of 150 bytes) before EOF is forcefully returned.

   Setting NLIMIT to 0 removes any active limit.

   Note: using iobuf_seek removes any currently enforced limit!  */

void iobuf_set_limit (iobuf_t a, off_t nlimit);

/* Returns the number of bytes that have been read from the pipeline.

   Note: the result is undefined for IOBUF_OUTPUT and IOBUF_OUTPUT_TEMP

   pipelines!  */

off_t iobuf_tell (iobuf_t a);

/* There are two cases:

   - If A is an INPUT or OUTPUT pipeline, then the last filter in the

     pipeline is found.  If that is not a file filter, -1 is returned.

     Otherwise, an fseek(..., SEEK_SET) is performed on the file

     descriptor.

   - If A is a TEMP pipeline and the *first* (and thus only filter) is

     a TEMP filter, then the "file position" is effectively unchanged.

     That is, data is appended to the buffer and the seek does not

     cause the size of the buffer to grow.

   If no error occurred, then any limit previous set by

   iobuf_set_limit() is cleared.  Further, any error on the filter

   (the file filter or the temp filter) is cleared.

   Returns 0 on success and -1 if an error occurs.  */

int iobuf_seek (iobuf_t a, off_t newpos);

/* Read a single byte.  If a filter has no more data, returns -1 to

   indicate the EOF.  Generally, you don't want to use this function,

   but instead prefer the iobuf_get macro, which is faster if there is

   data in the internal buffer.  */

int iobuf_readbyte (iobuf_t a);

/* Get a byte from the iobuf; must check for eof prior to this

   function.  This function returns values in the range 0 .. 255 or -1

   to indicate EOF.  iobuf_get_noeof() does not return -1 to indicate

   EOF, but masks the returned value to be in the range 0 .. 255.  */

#define iobuf_get(a)  \

     ( ((a)->nofast || (a)->d.start >= (a)->d.len )?  \

  iobuf_readbyte((a)) : ( (a)->nbytes++, (a)->d.buf[(a)->d.start++] ) )

#define iobuf_get_noeof(a)    (iobuf_get((a))&0xff)

/* Fill BUF with up to BUFLEN bytes.  If a filter has no more data,

   returns -1 to indicate the EOF.  Otherwise returns the number of

   bytes read.  */

int iobuf_read (iobuf_t a, void *buf, unsigned buflen);

/* Read a line of input (including the '\n') from the pipeline.

   The semantics are the same as for fgets(), but if the buffer is too

   short a larger one will be allocated up to *MAX_LENGTH and the end

   of the line except the trailing '\n' discarded.  (Thus,

   *ADDR_OF_BUFFER must be allocated using malloc().)  If the buffer

   is enlarged, then *LENGTH_OF_BUFFER will be updated to reflect the

   new size.  If the line is truncated, then *MAX_LENGTH will be set

   to 0.  If *ADDR_OF_BUFFER is NULL, a buffer is allocated using

   malloc().

   A line is considered a byte stream ending in a '\n'.  Returns the

   number of characters written to the buffer (i.e., excluding any

   discarded characters due to truncation).  Thus, use this instead of

   strlen(buffer) to determine the length of the string as this is

   unreliable if the input contains NUL characters.

   EOF is indicated by a line of length zero.

   The last LF may be missing due to an EOF.  */

unsigned iobuf_read_line (iobuf_t a, byte ** addr_of_buffer,

        unsigned *length_of_buffer, unsigned *max_length);

/* Read up to BUFLEN bytes from pipeline A.  Note: this function can't

   return more than the pipeline's internal buffer size.  The return

   value is the number of bytes actually written to BUF.  If the

   filter returns EOF, then this function returns -1.

   This function does not clear any pending EOF.  That is, if the

   pipeline consists of two filters and the first one returns EOF

   during the peek, then the subsequent iobuf_read* will still return

   EOF before returning the data from the second filter.  */

int iobuf_peek (iobuf_t a, byte * buf, unsigned buflen);

/* Write a byte to the pipeline.  Returns 0 on success and an error

   code otherwise.  */

int iobuf_writebyte (iobuf_t a, unsigned c);

/* Alias for iobuf_writebyte.  */

#define iobuf_put(a,c)  iobuf_writebyte(a,c)

/* Write a sequence of bytes to the pipeline.  Returns 0 on success

   and an error code otherwise.  */

int iobuf_write (iobuf_t a, const void *buf, unsigned buflen);

/* Write a string (not including the NUL terminator) to the pipeline.

   Returns 0 on success and an error code otherwise.  */

int iobuf_writestr (iobuf_t a, const char *buf);

/* Flushes the pipeline removing all filters but the sink (the last

   filter) in the process.  */

void iobuf_flush_temp (iobuf_t temp);

/* Flushes the pipeline SOURCE removing all filters but the sink (the

   last filter) in the process (i.e., it calls

   iobuf_flush_temp(source)) and then writes the data to the pipeline

   DEST.  Note: this doesn't free (iobuf_close()) SOURCE.  Both SOURCE

   and DEST must be output pipelines.  */

int iobuf_write_temp (iobuf_t dest, iobuf_t source);

/* Flushes each filter in the pipeline (i.e., sends any buffered data

   to the filter by calling IOBUFCTRL_FLUSH).  Then, copies up to the

   first BUFLEN bytes from the last filter's internal buffer (which

   will only be non-empty if it is a temp filter) to the buffer

   BUFFER.  Returns the number of bytes actually copied.  */

size_t iobuf_temp_to_buffer (iobuf_t a, byte * buffer, size_t buflen);

/* Copies the data from the input iobuf SOURCE to the output iobuf

   DEST until either an error is encountered or EOF is reached.

   Returns the number of bytes successfully written.  If an error

   occurred, then any buffered bytes are not returned to SOURCE and are

   effectively lost.  To check if an error occurred, use

   iobuf_error.  */

size_t iobuf_copy (iobuf_t dest, iobuf_t source);

/* Return the size of any underlying file.  This only works with

   file_filter based pipelines.  */

uint64_t iobuf_get_filelength (iobuf_t a);

#define IOBUF_FILELENGTH_LIMIT 0xffffffff

/* Return the file descriptor designating the underlying file.  This

   only works with file_filter based pipelines.  */

gnupg_fd_t iobuf_get_fd (iobuf_t a);

/* Return the real filename, if available.  This only supports

   pipelines that end in file filters.  Returns NULL if not

   available.  */

const char *iobuf_get_real_fname (iobuf_t a);

/* Return the filename or a description thereof.  For instance, for

   iobuf_open("-"), this will return "[stdin]".  This only supports

   pipelines that end in file filters.  Returns NULL if not

   available.  */

const char *iobuf_get_fname (iobuf_t a);

/* Like iobuf_getfname, but instead of returning NULL if no

   description is available, return "[?]".  */

const char *iobuf_get_fname_nonnull (iobuf_t a);

/* Pushes a filter on the pipeline that interprets the datastream as

   an OpenPGP data block whose length is encoded using partial body

   length headers (see Section 4.2.2.4 of RFC 4880).  Concretely, it

   just returns / writes the data and finishes the packet with an

   EOF.  */

void iobuf_set_partial_body_length_mode (iobuf_t a, size_t len);

/* If PARTIAL is set, then read from the pipeline until the first EOF

   is returned.

   If PARTIAL is 0, then read up to N bytes or until the first EOF is

   returned.

   Recall: a filter can return EOF.  In this case, it and all

   preceding filters are popped from the pipeline and the next read is

   from the following filter (which may or may not return EOF).  */

void iobuf_skip_rest (iobuf_t a, unsigned long n, int partial);

/* Check if the file is compressed, by peeking the iobuf.  */

int is_file_compressed (iobuf_t inp);

#define iobuf_where(a)  "[don't know]"

/* Each time a filter is allocated (via iobuf_alloc()), a

   monotonically increasing counter is incremented and this field is

   set to the new value.  This macro returns that number.  */

#define iobuf_id(a) ((a)->no)

#define iobuf_get_temp_buffer(a) ( (a)->d.buf )

#define iobuf_get_temp_length(a) ( (a)->d.len )

/* Whether the filter uses an in-memory buffer.  */

#define iobuf_is_temp(a)   ( (a)->use == IOBUF_OUTPUT_TEMP )

#endif /*GNUPG_COMMON_IOBUF_H*/