1 files changed, 159 insertions, 0 deletions
diff --git a/src/skaembutils/s6-head.c b/src/skaembutils/s6-head.c
new file mode 100644
index 0000000..1ef24c0
--- /dev/null
+++ b/src/skaembutils/s6-head.c
@@ -0,0 +1,159 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/sgetopt.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/uint.h>
+#include <skalibs/buffer.h>
+#include <skalibs/siovec.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/djbunix.h>
+
+#define USAGE "s6-head [ -S ] [ -1..9 | -n lines | -c chars ] [ file... ]"
+#define dieusage() strerr_dieusage(100, USAGE)
+
+typedef int headfunc_t (int, unsigned int) ;
+typedef headfunc_t *headfunc_t_ref ;
+
+static int dolines (int fd, unsigned int lines)
+{
+  char buf[BUFFER_INSIZE] ;
+  buffer in = BUFFER_INIT(&buffer_read, fd, buf, BUFFER_INSIZE) ;
+  buffer out = BUFFER_INIT(&buffer_write, 1, buf, BUFFER_INSIZE) ;
+  siovec_t v[2] ;
+  while (lines)
+  {
+    unsigned int w = 0 ;
+    register int r = buffer_fill(&in) ;
+    if (r <= 0) return !r ;
+    out.c.n = in.c.n ; out.c.p = in.c.p ;
+    buffer_rpeek(&in, v) ;
+    for (;;)
+    {
+      unsigned int n = siovec_len(v, 2) ;
+      register unsigned int i ;
+      if (!n) break ;
+      i = siovec_bytechr(v, 2, '\n') ;
+      if (i < n)
+      {
+        w += i+1 ;
+        siovec_seek(v, 2, i+1) ;
+        if (!--lines)
+        {
+          out.c.n = (out.c.p + w) % out.c.a ;
+          break ;
+        }
+      }
+      else siovec_seek(v, 2, i) ;
+    }
+    if (!buffer_flush(&out)) return 0 ;
+    in.c.n = out.c.n ; in.c.p = out.c.p ;
+  }
+  return 1 ;
+}
+
+static int safedolines (int fd, unsigned int lines)
+{
+  char tmp[lines] ;
+  while (lines)
+  {
+    unsigned int r = allread(fd, tmp, lines) ;
+    if ((r < lines) && (errno != EPIPE)) return 0 ;
+    lines -= byte_count(tmp, r, '\n') ;
+    if (buffer_put(buffer_1, tmp, r) < (int)r) return 0 ;
+  }
+  if (!buffer_flush(buffer_1)) return 0 ;
+  return 1 ;
+}
+
+static int safedochars (int fd, unsigned int chars)
+{
+  return (fd_catn(fd, 1, chars) >= chars) ;
+}
+
+int main (int argc, char const *const *argv)
+{
+  headfunc_t_ref f ;
+  unsigned int lines = 10 ;
+  int islines = 1, safe = 0 ;
+  PROG = "s6-head" ;
+  {
+    subgetopt_t l = SUBGETOPT_ZERO ;
+    int done = 0 ;
+    for (;;)
+    {
+      register int opt = subgetopt_r(argc, argv, "S123456789n:c:", &l) ;
+      if (opt == -1) break ;
+      switch (opt)
+      {
+        case 'S' : safe = 1 ; break ;
+        case '1' :
+        case '2' :
+        case '3' :
+        case '4' :
+        case '5' :
+        case '6' :
+        case '7' :
+        case '8' :
+        case '9' :
+        {
+          if (done) dieusage() ;
+          islines = 1 ;
+          lines = opt - '0' ;
+          done = 1 ;
+          break ;
+        }
+        case 'n' :
+        {
+          if (done || !uint0_scan(l.arg, &lines))
+            strerr_dieusage(100, USAGE) ;
+          islines = 1 ;
+          done = 1 ;
+          break ;
+        }
+        case 'c' :
+        {
+          if (done || !uint0_scan(l.arg, &lines))
+            strerr_dieusage(100, USAGE) ;
+          islines = 0 ;
+          done = 1 ;
+          break ;
+        }
+        default : strerr_dieusage(100, USAGE) ;
+      }
+    }
+    argc -= l.ind ; argv += l.ind ;
+  }
+  if (argc) safe = 0 ;
+  f = islines ? safe ? &safedolines : &dolines : &safedochars ;
+  if (!argc)
+  {
+    if (!(*f)(0, lines))
+      strerr_diefu1sys(111, "head stdin") ;
+  }
+  else
+  {
+    unsigned int i = 0 ;
+    for (; argv[i] ; i++)
+    {
+      int fd ;
+      if (argc >= 2)
+      {
+        if (i) buffer_putnoflush(buffer_1, "\n", 1) ;
+        buffer_putnoflush(buffer_1, "==> ", 4) ;
+        if ((buffer_puts(buffer_1, argv[i]) <= 0)
+         || (buffer_putflush(buffer_1, " <==\n", 5) < 0))
+          strerr_diefu1sys(111, "write to stdout") ;
+      }
+      if ((argv[i][0] == '-') && !argv[i][1]) fd = 0 ;
+      else fd = open_readb(argv[i]) ;
+      if (fd == -1)
+        strerr_diefu3sys(111, "open ", argv[i], " for reading") ;
+      if (!(*f)(fd, lines))
+        strerr_diefu2sys(111, "head ", argv[i]) ;
+      fd_close(fd) ;
+    }
+  }
+  return 0 ;
+}