pg: Initial support for receiving binary results

Just the initial framework stuff and a few types to test with.

c/pgtypes.c

@@ -0,0 +1,72 @@
+/* Send function, takes a Perl value and should write the binary encoded
+ * format into the given fustr. */
+typedef void (*fupg_send_fn)(pTHX_ SV *, fustr *, void *);
+
+/* Receive function, takes a binary string and should return a Perl value.
+ * libpq guarantees that the given buffer is aligned to MAXIMUM_ALIGNOF. */
+typedef SV *(*fupg_recv_fn)(pTHX_ const char *, int, void *);
+
+typedef struct {
+    Oid oid;
+    int len;
+    const char *name;
+    fupg_send_fn send;
+    fupg_recv_fn recv;
+} fupg_type;
+
+
+
+#define RECVFN(name) static SV *fupg_recv_##name(pTHX_ const char *buf, int buflen __attribute__((unused)), void *data __attribute__((unused)))
+
+RECVFN(textfmt) {
+    return newSVpvn_utf8(buf, buflen, 1);
+}
+
+RECVFN(bool) {
+    return *buf ? &PL_sv_yes : &PL_sv_no;
+}
+
+RECVFN(int2) {
+    return newSViv((I16)__builtin_bswap16(*((U16 *)buf)));
+}
+
+RECVFN(int4) {
+    return newSViv((I32)__builtin_bswap32(*((U32 *)buf)));
+}
+
+RECVFN(int8) {
+    return newSViv((I64)__builtin_bswap64(*((U64 *)buf)));
+}
+
+#undef RECVFN
+
+
+
+#define R(name) fupg_recv_##name
+
+/* Sorted by oid to support binary search.
+ * (XXX: hash lookup might be faster, but requires codegen) */
+static const fupg_type fupg_types[] = {
+    {  0, 0, NULL,   NULL, R(textfmt) }, /* Invalid Oid, abused for text format */
+    { 16, 1, "bool", NULL, R(bool)    },
+    { 20, 8, "int8", NULL, R(int8)    },
+    { 21, 2, "int2", NULL, R(int2)    },
+    { 23, 4, "int4", NULL, R(int4)    },
+};
+/* TODO: A LOT MORE TYPES */
+
+#undef R
+
+#define FUPG_TYPES (sizeof(fupg_types) / sizeof(fupg_type))
+
+
+static const fupg_type *fupg_type_lookup(Oid oid) {
+    int i, b = 0, e = FUPG_TYPES-1;
+    while (b <= e) {
+        i = b + (e - b)/2;
+        if (fupg_types[i].oid == oid) return fupg_types+i;
+        if (fupg_types[i].oid < oid) b = i+1;
+        else e = i-1;
+    }
+    return NULL;
+}