1 files changed, 25 insertions, 0 deletions
diff --git a/src/libstddjb/env_merge.c b/src/libstddjb/env_merge.c
new file mode 100644
index 0000000..2a0e5bd
--- /dev/null
+++ b/src/libstddjb/env_merge.c
@@ -0,0 +1,25 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/env.h>
+
+unsigned int env_merge (char const **v, unsigned int vmax, char const *const *envp, unsigned int envlen, char const *modifs, unsigned int modiflen)
+{
+  unsigned int n = byte_count(modifs, modiflen, '\0') ;
+  unsigned int vlen = envlen ;
+  register unsigned int i = 0 ;
+  if (envlen + n + 1 > vmax) return (errno = ENAMETOOLONG, 0) ;
+  for (; i < envlen ; i++) v[i] = envp[i] ;
+  for (i = 0 ; i < modiflen ; i += str_len(modifs + i) + 1)
+  {
+    unsigned int split = str_chr(modifs + i, '=') ;
+    register unsigned int j = 0 ;
+    for (; j < vlen ; j++)
+      if (!byte_diff(modifs + i, split, v[j]) && (v[j][split] == '=')) break ;
+    if (j < vlen) v[j] = v[--vlen] ;
+    if (modifs[i + split]) v[vlen++] = modifs + i ;
+  }
+  v[vlen++] = 0 ;
+  return vlen ;
+}