[PATCH 3/8] digest: refactor sum(1) into digest.c

[Pádraig Brady]

Since digest will be providing all digest functionality,
refactor sum.c into it.

* po/POTFILES.in: sum.c no longer has translatable strings so remove.
* src/digest.c: Call out to new stream interfaces in sum.c
* src/local.mk: Adjust sources for the sum binary.
* src/sum.c: Provide a stream interface for BSD and SYSV digests.
* src/sum.h: A new file to declare the exported functions in sum.c
---
 po/POTFILES.in |   1 -
 src/digest.c   | 188 ++++++++++++++++++++---------
 src/local.mk   |   3 +
 src/sum.c      | 318 ++++++++++++++++++-------------------------------
 src/sum.h      |  16 +++
 5 files changed, 272 insertions(+), 254 deletions(-)
 create mode 100644 src/sum.h

diff --git a/po/POTFILES.in b/po/POTFILES.in
index de70201a0..aca7c260f 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -120,7 +120,6 @@ src/split.c
 src/stat.c
 src/stdbuf.c
 src/stty.c
-src/sum.c
 src/sync.c
 src/system.h
 src/tac-pipe.c
diff --git a/src/digest.c b/src/digest.c
index 97804de0f..090ba73d7 100644
--- a/src/digest.c
+++ b/src/digest.c
@@ -27,6 +27,9 @@
 #include "xdectoint.h"
 #include "xstrtol.h"
 
+#if HASH_ALGO_SUM
+# include "sum.h"
+#endif
 #if HASH_ALGO_BLAKE2
 # include "blake2/b2sum.h"
 #endif
@@ -49,7 +52,14 @@
 #include "xbinary-io.h"
 
 /* The official name of this program (e.g., no 'g' prefix).  */
-#if HASH_ALGO_MD5
+#if HASH_ALGO_SUM
+# define PROGRAM_NAME "sum"
+# define DIGEST_TYPE_STRING "BSD"
+# define DIGEST_STREAM sumfns[sum_algorithm]
+# define DIGEST_OUT sum_output_fns[sum_algorithm]
+# define DIGEST_BITS 16
+# define DIGEST_ALIGN 4
+#elif HASH_ALGO_MD5
 # define PROGRAM_NAME "md5sum"
 # define DIGEST_TYPE_STRING "MD5"
 # define DIGEST_STREAM md5_stream
@@ -101,8 +111,15 @@
 #else
 # error "Can't decide which hash algorithm to compile."
 #endif
+#if !HASH_ALGO_SUM
+# define DIGEST_OUT output_file
+#endif
 
-#if HASH_ALGO_BLAKE2
+#if HASH_ALGO_SUM
+# define AUTHORS \
+  proper_name ("Kayvan Aghaiepour"), \
+  proper_name ("David MacKenzie")
+#elif HASH_ALGO_BLAKE2
 # define AUTHORS \
   proper_name ("Padraig Brady"), \
   proper_name ("Samuel Neves")
@@ -111,6 +128,8 @@
   proper_name ("Ulrich Drepper"), \
   proper_name ("Scott Miller"), \
   proper_name ("David Madore")
+#endif
+#if !HASH_ALGO_BLAKE2
 # define DIGEST_HEX_BYTES (DIGEST_BITS / 4)
 #endif
 #define DIGEST_BIN_BYTES (DIGEST_BITS / 8)
@@ -188,6 +207,28 @@ static uintmax_t blake2_max_len[]=
 };
 #endif /* HASH_ALGO_BLAKE2 */
 
+typedef void (*digest_output_fn)(char const*, int, void const*,
+                                 bool, bool, uintmax_t);
+#if HASH_ALGO_SUM
+enum Algorithm
+{
+  bsd,
+  sysv,
+};
+
+static enum Algorithm sum_algorithm;
+static sumfn sumfns[]=
+{
+  bsd_sum_stream,
+  sysv_sum_stream,
+};
+static digest_output_fn sum_output_fns[]=
+{
+  output_bsd,
+  output_sysv,
+};
+#endif
+
 /* For long options that have no equivalent short option, use a
    non-character as a pseudo short option, starting with CHAR_MAX + 1.  */
 enum
@@ -204,6 +245,7 @@ static struct option const long_options[] =
 #if HASH_ALGO_BLAKE2
   { "length", required_argument, NULL, 'l'},
 #endif
+#if !HASH_AGLO_SUM
   { "binary", no_argument, NULL, 'b' },
   { "check", no_argument, NULL, 'c' },
   { "ignore-missing", no_argument, NULL, IGNORE_MISSING_OPTION},
@@ -214,6 +256,9 @@ static struct option const long_options[] =
   { "strict", no_argument, NULL, STRICT_OPTION },
   { "tag", no_argument, NULL, TAG_OPTION },
   { "zero", no_argument, NULL, 'z' },
+#else
+  {"sysv", no_argument, NULL, 's'},
+#endif
   { GETOPT_HELP_OPTION_DECL },
   { GETOPT_VERSION_OPTION_DECL },
   { NULL, 0, NULL, 0 }
@@ -235,6 +280,13 @@ Print or check %s (%d-bit) checksums.\n\
               DIGEST_BITS);
 
       emit_stdin_note ();
+#if HASH_ALGO_SUM
+      fputs (_("\
+\n\
+  -r              use BSD sum algorithm (the default), use 1K blocks\n\
+  -s, --sysv      use System V sum algorithm, use 512 bytes blocks\n\
+"), stdout);
+#else
       if (O_BINARY)
         fputs (_("\
 \n\
@@ -249,12 +301,12 @@ Print or check %s (%d-bit) checksums.\n\
       printf (_("\
   -c, --check          read %s sums from the FILEs and check them\n"),
               DIGEST_TYPE_STRING);
-#if HASH_ALGO_BLAKE2
+# if HASH_ALGO_BLAKE2
         fputs (_("\
   -l, --length         digest length in bits; must not exceed the maximum 
for\n\
                        the blake2 algorithm and must be a multiple of 8\n\
 "), stdout);
-#endif
+# endif
       fputs (_("\
       --tag            create a BSD-style checksum\n\
 "), stdout);
@@ -280,8 +332,10 @@ The following five options are useful only when verifying 
checksums:\n\
   -w, --warn           warn about improperly formatted checksum lines\n\
 \n\
 "), stdout);
+#endif
       fputs (HELP_OPTION_DESCRIPTION, stdout);
       fputs (VERSION_OPTION_DESCRIPTION, stdout);
+#if !HASH_ALGO_SUM
       printf (_("\
 \n\
 The sums are computed as described in %s.  When checking, the input\n\
@@ -292,6 +346,7 @@ line with checksum, a space, a character indicating input 
mode ('*' for binary,\
 Note: There is no difference between binary mode and text mode on GNU systems.\
 \n"),
               DIGEST_REFERENCE);
+#endif
       emit_ancillary_info (PROGRAM_NAME);
     }
 
@@ -626,7 +681,9 @@ digest_file (char const *filename, int *binary, unsigned 
char *bin_result,
 
   fadvise (fp, FADVISE_SEQUENTIAL);
 
-#if HASH_ALGO_BLAKE2
+#if HASH_ALGO_SUM
+  err = DIGEST_STREAM (fp, bin_result, length);
+#elif HASH_ALGO_BLAKE2
   err = DIGEST_STREAM (fp, bin_result, b2_length / 8);
 #else
   err = DIGEST_STREAM (fp, bin_result);
@@ -646,6 +703,60 @@ digest_file (char const *filename, int *binary, unsigned 
char *bin_result,
   return true;
 }
 
+#if !HASH_ALGO_SUM
+static void
+output_file (char const *file, int binary_file, void const *digest,
+             bool tagged, bool args _GL_UNUSED, uintmax_t length _GL_UNUSED)
+{
+  unsigned char const *bin_buffer = digest;
+  /* We don't really need to escape, and hence detect, the '\\'
+      char, and not doing so should be both forwards and backwards
+      compatible, since only escaped lines would have a '\\' char at
+      the start.  However just in case users are directly comparing
+      against old (hashed) outputs, in the presence of files
+      containing '\\' characters, we decided to not simplify the
+      output in this case.  */
+  bool needs_escape = (strchr (file, '\\') || strchr (file, '\n'))
+                      && delim == '\n';
+
+  if (tagged)
+    {
+      if (needs_escape)
+        putchar ('\\');
+
+# if HASH_ALGO_BLAKE2
+      fputs (algorithm_out_string[b2_algorithm], stdout);
+      if (b2_length < blake2_max_len[b2_algorithm] * 8)
+        printf ("-%"PRIuMAX, b2_length);
+# else
+      fputs (DIGEST_TYPE_STRING, stdout);
+# endif
+      fputs (" (", stdout);
+      print_filename (file, needs_escape);
+      fputs (") = ", stdout);
+    }
+
+  /* Output a leading backslash if the file name contains
+      a newline or backslash.  */
+  if (!tagged && needs_escape)
+    putchar ('\\');
+
+  for (size_t i = 0; i < (digest_hex_bytes / 2); ++i)
+    printf ("%02x", bin_buffer[i]);
+
+  if (!tagged)
+    {
+      putchar (' ');
+
+      putchar (binary_file ? '*' : ' ');
+
+      print_filename (file, needs_escape);
+    }
+
+  putchar (delim);
+}
+#endif
+
 static bool
 digest_check (char const *checkfile_name)
 {
@@ -881,7 +992,9 @@ main (int argc, char **argv)
      so that processes running in parallel do not intersperse their output.  */
   setvbuf (stdout, NULL, _IOLBF, 0);
 
-#if HASH_ALGO_BLAKE2
+#if HASH_ALGO_SUM
+  const char* short_opts = "rs";
+#elif HASH_ALGO_BLAKE2
   const char* short_opts = "l:bctwz";
   const char* b2_length_str = "";
 #else
@@ -903,6 +1016,7 @@ main (int argc, char **argv)
           }
         break;
 #endif
+#if !HASH_ALGO_SUM
       case 'b':
         binary = 1;
         break;
@@ -940,6 +1054,15 @@ main (int argc, char **argv)
       case 'z':
         delim = '\0';
         break;
+#else
+      case 'r':                /* For SysV compatibility. */
+        sum_algorithm = bsd;
+        break;
+
+      case 's':
+        sum_algorithm = sysv;
+        break;
+#endif
       case_GETOPT_HELP_CHAR;
       case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
       default:
@@ -1041,63 +1164,20 @@ main (int argc, char **argv)
   for (char **operandp = argv + optind; operandp < operand_lim; operandp++)
     {
       char *file = *operandp;
-
       if (do_check)
         ok &= digest_check (file);
       else
         {
-          int file_is_binary = binary;
+          int binary_file = binary;
           bool missing;
+          uintmax_t length;
 
-          if (! digest_file (file, &file_is_binary, bin_buffer, &missing, 
NULL))
+          if (! digest_file (file, &binary_file, bin_buffer, &missing, 
&length))
             ok = false;
           else
             {
-              /* We don't really need to escape, and hence detect, the '\\'
-                 char, and not doing so should be both forwards and backwards
-                 compatible, since only escaped lines would have a '\\' char at
-                 the start.  However just in case users are directly comparing
-                 against old (hashed) outputs, in the presence of files
-                 containing '\\' characters, we decided to not simplify the
-                 output in this case.  */
-              bool needs_escape = (strchr (file, '\\') || strchr (file, '\n'))
-                                  && delim == '\n';
-
-              if (prefix_tag)
-                {
-                  if (needs_escape)
-                    putchar ('\\');
-
-#if HASH_ALGO_BLAKE2
-                  fputs (algorithm_out_string[b2_algorithm], stdout);
-                  if (b2_length < blake2_max_len[b2_algorithm] * 8)
-                    printf ("-%"PRIuMAX, b2_length);
-#else
-                  fputs (DIGEST_TYPE_STRING, stdout);
-#endif
-                  fputs (" (", stdout);
-                  print_filename (file, needs_escape);
-                  fputs (") = ", stdout);
-                }
-
-              /* Output a leading backslash if the file name contains
-                 a newline or backslash.  */
-              if (!prefix_tag && needs_escape)
-                putchar ('\\');
-
-              for (size_t i = 0; i < (digest_hex_bytes / 2); ++i)
-                printf ("%02x", bin_buffer[i]);
-
-              if (!prefix_tag)
-                {
-                  putchar (' ');
-
-                  putchar (file_is_binary ? '*' : ' ');
-
-                  print_filename (file, needs_escape);
-                }
-
-              putchar (delim);
+              DIGEST_OUT (file, binary_file, bin_buffer, prefix_tag,
+                          optind != argc, length);
             }
         }
     }
diff --git a/src/local.mk b/src/local.mk
index bb5b722f2..b1fce9c27 100644
--- a/src/local.mk
+++ b/src/local.mk
@@ -355,6 +355,9 @@ src___SOURCES = src/lbracket.c
 nodist_src_coreutils_SOURCES = src/coreutils.h
 src_coreutils_SOURCES = src/coreutils.c
 
+src_sum_SOURCES = src/sum.c src/sum.h src/digest.c
+src_sum_CPPFLAGS = -DHASH_ALGO_SUM=1 $(AM_CPPFLAGS)
+
 src_cksum_SOURCES = src/cksum.c src/cksum.h
 if USE_PCLMUL_CRC32
 noinst_LIBRARIES += src/libcksum_pclmul.a
diff --git a/src/sum.c b/src/sum.c
index c66147edc..1633c86c5 100644
--- a/src/sum.c
+++ b/src/sum.c
@@ -22,251 +22,171 @@
 
 #include <stdio.h>
 #include <sys/types.h>
-#include <getopt.h>
 #include "system.h"
-#include "die.h"
-#include "error.h"
-#include "fadvise.h"
 #include "human.h"
-#include "safe-read.h"
-#include "xbinary-io.h"
+#include "sum.h"
 
-/* The official name of this program (e.g., no 'g' prefix).  */
-#define PROGRAM_NAME "sum"
+/* Calculate the checksum and the size in bytes of stream STREAM.
+   Return -1 on error, 0 on success.  */
 
-#define AUTHORS \
-  proper_name ("Kayvan Aghaiepour"), \
-  proper_name ("David MacKenzie")
+int
+bsd_sum_stream (FILE *stream, void *resstream, uintmax_t *length)
+{
+  int ret = -1;
+  size_t sum, n;
+  int checksum = 0;    /* The checksum mod 2^16. */
+  uintmax_t total_bytes = 0;   /* The number of bytes. */
+  static const size_t buffer_length = 32768;
+  uint8_t *buffer = malloc (buffer_length);
 
-/* True if any of the files read were the standard input. */
-static bool have_read_stdin;
+  if (! buffer)
+    return -1;
 
-static struct option const longopts[] =
-{
-  {"sysv", no_argument, NULL, 's'},
-  {GETOPT_HELP_OPTION_DECL},
-  {GETOPT_VERSION_OPTION_DECL},
-  {NULL, 0, NULL, 0}
-};
+  /* Process file */
+  while (true)
+  {
+    sum = 0;
 
-void
-usage (int status)
-{
-  if (status != EXIT_SUCCESS)
-    emit_try_help ();
-  else
+    /* Read block */
+    while (true)
     {
-      printf (_("\
-Usage: %s [OPTION]... [FILE]...\n\
-"),
-              program_name);
-      fputs (_("\
-Print checksum and block counts for each FILE.\n\
-"), stdout);
-
-      emit_stdin_note ();
-
-      fputs (_("\
-\n\
-  -r              use BSD sum algorithm (the default), use 1K blocks\n\
-  -s, --sysv      use System V sum algorithm, use 512 bytes blocks\n\
-"), stdout);
-      fputs (HELP_OPTION_DESCRIPTION, stdout);
-      fputs (VERSION_OPTION_DESCRIPTION, stdout);
-      emit_ancillary_info (PROGRAM_NAME);
-    }
-  exit (status);
-}
-
-/* Calculate and print the rotated checksum and the size in 1K blocks
-   of file FILE, or of the standard input if FILE is "-".
-   If PRINT_NAME is >0, print FILE next to the checksum and size.
-   The checksum varies depending on sizeof (int).
-   Return true if successful.  */
+      n = fread (buffer + sum, 1, buffer_length - sum, stream);
+      sum += n;
 
-static bool
-bsd_sum_file (char const *file, int print_name)
-{
-  FILE *fp;
-  int checksum = 0;    /* The checksum mod 2^16. */
-  uintmax_t total_bytes = 0;   /* The number of bytes. */
-  int ch;              /* Each character read. */
-  char hbuf[LONGEST_HUMAN_READABLE + 1];
-  bool is_stdin = STREQ (file, "-");
+      if (buffer_length == sum)
+        break;
 
-  if (is_stdin)
-    {
-      fp = stdin;
-      have_read_stdin = true;
-      xset_binary_mode (STDIN_FILENO, O_BINARY);
-    }
-  else
-    {
-      fp = fopen (file, (O_BINARY ? "rb" : "r"));
-      if (fp == NULL)
+      if (n == 0)
         {
-          error (0, errno, "%s", quotef (file));
-          return false;
+          if (ferror (stream))
+            goto cleanup_buffer;
+          goto final_process;
         }
+
+      if (feof (stream))
+        goto final_process;
     }
 
-  fadvise (fp, FADVISE_SEQUENTIAL);
+    for (size_t i = 0; i < sum; i++)
+      {
+        checksum = (checksum >> 1) + ((checksum & 1) << 15);
+        checksum += buffer[i];
+        checksum &= 0xffff;    /* Keep it within bounds. */
+      }
+    total_bytes += sum;
+  }
 
-  while ((ch = getc (fp)) != EOF)
+final_process:;
+
+  for (size_t i = 0; i < sum; i++)
     {
-      total_bytes++;
       checksum = (checksum >> 1) + ((checksum & 1) << 15);
-      checksum += ch;
+      checksum += buffer[i];
       checksum &= 0xffff;      /* Keep it within bounds. */
     }
-
-  int err = errno;
-  if (!ferror (fp))
-    err = 0;
-  if (is_stdin)
-    clearerr (fp);
-  else if (fclose (fp) != 0 && !err)
-    err = errno;
-  if (err)
-    {
-      error (0, err, "%s", quotef (file));
-      return false;
-    }
-
-  printf ("%05d %5s", checksum,
-          human_readable (total_bytes, hbuf, human_ceiling, 1, 1024));
-  if (print_name)
-    printf (" %s", file);
-  putchar ('\n');
-
-  return true;
+  total_bytes += sum;
+
+  memcpy (resstream, &checksum, sizeof checksum);
+  *length = total_bytes;
+  ret = 0;
+cleanup_buffer:
+  free (buffer);
+  return ret;
 }
 
-/* Calculate and print the checksum and the size in 512-byte blocks
-   of file FILE, or of the standard input if FILE is "-".
-   If PRINT_NAME is >0, print FILE next to the checksum and size.
-   Return true if successful.  */
+/* Calculate the checksum and the size in bytes of stream STREAM.
+   Return -1 on error, 0 on success.  */
 
-static bool
-sysv_sum_file (char const *file, int print_name)
+int
+sysv_sum_stream (FILE *stream, void *resstream, uintmax_t *length)
 {
-  int fd;
-  unsigned char buf[8192];
+  int ret = -1;
+  size_t sum, n;
   uintmax_t total_bytes = 0;
-  char hbuf[LONGEST_HUMAN_READABLE + 1];
-  int r;
-  int checksum;
+  static const size_t buffer_length = 32768;
+  uint8_t *buffer = malloc (buffer_length);
+
+  if (! buffer)
+    return -1;
 
   /* The sum of all the input bytes, modulo (UINT_MAX + 1).  */
   unsigned int s = 0;
 
-  bool is_stdin = STREQ (file, "-");
-
-  if (is_stdin)
-    {
-      fd = STDIN_FILENO;
-      have_read_stdin = true;
-      xset_binary_mode (STDIN_FILENO, O_BINARY);
-    }
-  else
-    {
-      fd = open (file, O_RDONLY | O_BINARY);
-      if (fd == -1)
-        {
-          error (0, errno, "%s", quotef (file));
-          return false;
-        }
-    }
-
+  /* Process file */
   while (true)
+  {
+    sum = 0;
+
+    /* Read block */
+    while (true)
     {
-      size_t bytes_read = safe_read (fd, buf, sizeof buf);
+      n = fread (buffer + sum, 1, buffer_length - sum, stream);
+      sum += n;
 
-      if (bytes_read == 0)
+      if (buffer_length == sum)
         break;
 
-      if (bytes_read == SAFE_READ_ERROR)
+      if (n == 0)
         {
-          error (0, errno, "%s", quotef (file));
-          if (!is_stdin)
-            close (fd);
-          return false;
+          if (ferror (stream))
+            goto cleanup_buffer;
+          goto final_process;
         }
 
-      for (size_t i = 0; i < bytes_read; i++)
-        s += buf[i];
-      total_bytes += bytes_read;
-    }
-
-  if (!is_stdin && close (fd) != 0)
-    {
-      error (0, errno, "%s", quotef (file));
-      return false;
+      if (feof (stream))
+        goto final_process;
     }
 
-  r = (s & 0xffff) + ((s & 0xffffffff) >> 16);
-  checksum = (r & 0xffff) + (r >> 16);
-
-  printf ("%d %s", checksum,
-          human_readable (total_bytes, hbuf, human_ceiling, 1, 512));
-  if (print_name)
-    printf (" %s", file);
-  putchar ('\n');
-
-  return true;
-}
-
-int
-main (int argc, char **argv)
-{
-  bool ok;
-  int optc;
-  int files_given;
-  bool (*sum_func) (char const *, int) = bsd_sum_file;
-
-  initialize_main (&argc, &argv);
-  set_program_name (argv[0]);
-  setlocale (LC_ALL, "");
-  bindtextdomain (PACKAGE, LOCALEDIR);
-  textdomain (PACKAGE);
+    for (size_t i = 0; i < sum; i++)
+      s += buffer[i];
+    total_bytes += sum;
+  }
 
-  atexit (close_stdout);
+final_process:;
 
-  /* Line buffer stdout to ensure lines are written atomically and immediately
-     so that processes running in parallel do not intersperse their output.  */
-  setvbuf (stdout, NULL, _IOLBF, 0);
+  for (size_t i = 0; i < sum; i++)
+    s += buffer[i];
+  total_bytes += sum;
 
-  have_read_stdin = false;
+  int r = (s & 0xffff) + ((s & 0xffffffff) >> 16);
+  int checksum = (r & 0xffff) + (r >> 16);
 
-  while ((optc = getopt_long (argc, argv, "rs", longopts, NULL)) != -1)
-    {
-      switch (optc)
-        {
-        case 'r':              /* For SysV compatibility. */
-          sum_func = bsd_sum_file;
-          break;
+  memcpy (resstream, &checksum, sizeof checksum);
+  *length = total_bytes;
+  ret = 0;
+cleanup_buffer:
+  free (buffer);
+  return ret;
+}
 
-        case 's':
-          sum_func = sysv_sum_file;
-          break;
+/* Print the checksum and size (in 1024 byte blocks) to stdout.
+   If ARGS is true, also print the FILE name.  */
 
-        case_GETOPT_HELP_CHAR;
+void
+output_bsd (char const *file, int binary_file, void const *digest,
+            bool tagged, bool args _GL_UNUSED, uintmax_t length _GL_UNUSED)
+{
 
-        case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
+  char hbuf[LONGEST_HUMAN_READABLE + 1];
+  printf ("%05d %5s", *(int *)digest,
+          human_readable (length, hbuf, human_ceiling, 1, 1024));
+  if (args)
+    printf (" %s", file);
+  putchar ('\n');
+}
 
-        default:
-          usage (EXIT_FAILURE);
-        }
-    }
+/* Print the checksum and size (in 512 byte blocks) to stdout.
+   If ARGS is true, also print the FILE name.  */
 
-  files_given = argc - optind;
-  if (files_given <= 0)
-    ok = sum_func ("-", files_given);
-  else
-    for (ok = true; optind < argc; optind++)
-      ok &= sum_func (argv[optind], files_given);
+void
+output_sysv (char const *file, int binary_file, void const *digest,
+             bool tagged, bool args _GL_UNUSED, uintmax_t length _GL_UNUSED)
+{
 
-  if (have_read_stdin && fclose (stdin) == EOF)
-    die (EXIT_FAILURE, errno, "%s", quotef ("-"));
-  return ok ? EXIT_SUCCESS : EXIT_FAILURE;
+  char hbuf[LONGEST_HUMAN_READABLE + 1];
+  printf ("%d %s", *(int *)digest,
+          human_readable (length, hbuf, human_ceiling, 1, 512));
+  if (args)
+    printf (" %s", file);
+  putchar ('\n');
 }
diff --git a/src/sum.h b/src/sum.h
new file mode 100644
index 000000000..ca68f750a
--- /dev/null
+++ b/src/sum.h
@@ -0,0 +1,16 @@
+extern int
+bsd_sum_stream (FILE *stream, void *resstream, uintmax_t *length);
+
+extern int
+sysv_sum_stream (FILE *stream, void *resstream, uintmax_t *length);
+
+typedef int (*sumfn)(FILE *, void *, uintmax_t*);
+
+
+extern void
+output_bsd (char const *file, int binary_file, void const *digest,
+            bool tagged, bool args _GL_UNUSED, uintmax_t length _GL_UNUSED);
+
+extern void
+output_sysv (char const *file, int binary_file, void const *digest,
+             bool tagged, bool args _GL_UNUSED, uintmax_t length _GL_UNUSED);
-- 
2.26.2