1 files changed, 61 insertions, 0 deletions
diff --git a/src/libenvexec/child_spawn.c b/src/libenvexec/child_spawn.c
new file mode 100644
index 0000000..164f1b2
--- /dev/null
+++ b/src/libenvexec/child_spawn.c
@@ -0,0 +1,61 @@
+/* ISC license. */
+
+#include <string.h>
+#include <unistd.h>
+
+#include <skalibs/types.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/env.h>
+#include <skalibs/cspawn.h>
+
+pid_t child_spawn (char const *prog, char const *const *argv, char const *const *envp, int *fds, size_t n)
+{
+  pid_t pid ;
+  cspawn_fileaction fa[2] =
+  {
+    [0] = { .type = CSPAWN_FA_MOVE, .x = { .fd2 = { [0] = 1 } } },
+    [1] = { .type = CSPAWN_FA_MOVE, .x = { .fd2 = { [0] = 0 } } }
+  } ;
+  size_t m = sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) ;
+  size_t envlen = env_len(envp) ;
+  size_t i = 0 ;
+  int p[n ? n : 1][2] ;
+  char const *newenv[envlen + 2] ;
+  char modifs[m + 1 + n * UINT_FMT] ;
+
+  for (; i < n ; i++)
+  {
+    if (pipe(p[i]) == -1) goto errpi ;
+    if ((ndelay_on(p[i][i & 1]) == -1) || (coe(p[i][i & 1]) == -1)) goto errpip ;
+  }
+
+  memcpy(modifs, SKALIBS_CHILD_SPAWN_FDS_ENVVAR "=", sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR)) ;
+  for (i = 2 ; i < n ; i++)
+  {
+    m += uint_fmt(modifs + m, p[i][!(i & 1)]) ;
+    if (i+1 < n) modifs[m++] = ',' ;
+  }
+  modifs[m++] = 0 ;
+  env_mergen(newenv, envlen + 2, envp, envlen, modifs, m, 1) ;
+  if (n) fa[0].x.fd2[1] = p[0][1] ;
+  if (n >= 2) fa[1].x.fd2[1] = p[1][0] ;
+  pid = cspawn(prog, argv, newenv, CSPAWN_FLAGS_SIGBLOCKNONE, fa, n < 2 ? n : 2) ;
+  if (!pid) goto errpi ;
+
+  for (i = 0 ; i < n ; i++)
+  {
+    fd_close(p[i][!(i & 1)]) ;
+    fds[i] = p[i][i & 1] ;
+  }
+  return pid ;
+
+ errpip:
+  i++ ;
+ errpi:
+  while (i--)
+  {
+    fd_close(p[i][1]) ;
+    fd_close(p[i][0]) ;
+  }
+  return 0 ;
+}