add iconv framework for decoding stateful encodings

assuming pointers obtained from malloc have some nonzero alignment,
repurpose the low bit of iconv_t as an indicator that the descriptor
is a stateless value representing the source and destination character
encodings.

diff --git a/src/locale/iconv.c b/src/locale/iconv.c
index fd51b73..0696b55 100644 (file)
--- a/src/locale/iconv.c
+++ b/src/locale/iconv.c
@@ -100,9 +100,14 @@ static size_t find_charmap(const void *name)
        return -1;
 }
 
+struct stateful_cd {
+       iconv_t base_cd;
+       unsigned state;
+};
+
 static iconv_t combine_to_from(size_t t, size_t f)
 {
-       return (void *)(f<<16 | t);
+       return (void *)(f<<16 | t<<1 | 1);
 }
 
 static size_t extract_from(iconv_t cd)
@@ -112,7 +117,7 @@ static size_t extract_from(iconv_t cd)
 
 static size_t extract_to(iconv_t cd)
 {
-       return (size_t)cd & 0xffff;
+       return (size_t)cd >> 1 & 0x7fff;
 }
 
 iconv_t iconv_open(const char *to, const char *from)
@@ -125,8 +130,17 @@ iconv_t iconv_open(const char *to, const char *from)
                errno = EINVAL;
                return (iconv_t)-1;
        }
+       iconv_t cd = combine_to_from(t, f);
 
-       return combine_to_from(t, f);
+       if (0) {
+               struct stateful_cd *scd = malloc(sizeof *scd);
+               if (!scd) return (iconv_t)-1;
+               scd->base_cd = cd;
+               scd->state = 0;
+               cd = (iconv_t)scd;
+       }
+
+       return cd;
 }
 
 static unsigned get_16(const unsigned char *s, int e)
@@ -172,6 +186,11 @@ static unsigned legacy_map(const unsigned char *map, unsigned c)
 size_t iconv(iconv_t cd, char **restrict in, size_t *restrict inb, char **restrict out, size_t *restrict outb)
 {
        size_t x=0;
+       struct stateful_cd *scd=0;
+       if (!((size_t)cd & 1)) {
+               scd = (void *)cd;
+               cd = scd->base_cd;
+       }
        unsigned to = extract_to(cd);
        unsigned from = extract_from(cd);
        const unsigned char *map = charmaps+from+1;

diff --git a/src/locale/iconv_close.c b/src/locale/iconv_close.c
index fac681c..28b2956 100644 (file)
--- a/src/locale/iconv_close.c
+++ b/src/locale/iconv_close.c
@@ -1,6 +1,8 @@
 #include <iconv.h>
+#include <stdlib.h>
 
 int iconv_close(iconv_t cd)
 {
+       if (!((size_t)cd & 1)) free((void *)cd);
        return 0;
 }