optimize the reading of strings in the grammar loader.

src/runtime/c/gu/in.c

@@ -253,7 +253,6 @@ gu_in_f64be(GuIn* in, GuExn* err)
 	return gu_decode_double(gu_in_u64le(in, err));
 }
 
-
 static void
 gu_in_fini(GuFinalizer* fin)
 {

src/runtime/c/gu/string.c

@@ -5,6 +5,7 @@
 #include <gu/string.h>
 #include <gu/utf8.h>
 #include <gu/assert.h>
+#include <stdlib.h>
 
 const GuString gu_empty_string = { 1 };
 
@@ -165,6 +166,43 @@ gu_string_write(GuString s, GuOut* out, GuExn* err)
 	gu_out_bytes(out, src, sz, err);
 }
 
+GuString
+gu_string_read(size_t len, GuPool* pool, GuIn* in, GuExn* err)
+{
+	uint8_t* buf = alloca(len*4);
+	uint8_t* p   = buf;
+	for (size_t i = 0; i < len; i++) {
+		gu_in_utf8_buf(&p, in, err);
+	}
+	return gu_utf8_string(buf, p-buf, pool);
+}
+
+GuString
+gu_string_read_latin1(size_t len, GuPool* pool, GuIn* in, GuExn* err)
+{
+	if (len < GU_MIN(sizeof(GuWord), 128)) {
+		GuWord w = 0;
+		for (size_t n = 0; n < len; n++) {
+			w = w << 8 | gu_in_u8(in, err);
+		}
+		w = w << 8 | (len << 1) | 1;
+		return (GuString) { w };
+	}
+	uint8_t* p = NULL;
+	if (len < 256) {
+		p = gu_malloc_aligned(pool, 1 + len, 2);
+		p[0] = (uint8_t) len;
+	} else {
+		p =	gu_malloc_prefixed(pool, gu_alignof(size_t),
+		                       sizeof(size_t), 1, 1 + len);
+		((size_t*) p)[-1] = len;
+		p[0] = 0;
+	}
+
+	gu_in_bytes(in, &p[1], len, err);
+	return (GuString) { (GuWord) (void*) p };
+}
+
 GuString
 gu_format_string_v(const char* fmt, va_list args, GuPool* pool)
 {

src/runtime/c/gu/string.h

@@ -34,6 +34,12 @@ gu_string_copy(GuString string, GuPool* pool);
 void
 gu_string_write(GuString string, GuOut* out, GuExn* err);
 
+GuString
+gu_string_read(size_t len, GuPool* pool, GuIn* in, GuExn* err);
+
+GuString
+gu_string_read_latin1(size_t len, GuPool* pool, GuIn* in, GuExn* err);
+
 GuIn*
 gu_string_in(GuString string, GuPool* pool);
 

src/runtime/c/gu/utf8.c

@@ -72,8 +72,8 @@ fail:
 	return 0;
 }
 
-extern inline void
-gu_out_utf8(GuUCS ucs, GuOut* out, GuExn* err);
+extern inline GuUCS
+gu_in_utf8(GuIn* in, GuExn* err);
 
 static size_t
 gu_advance_utf8(GuUCS ucs, uint8_t* buf)
@@ -121,5 +121,46 @@ gu_out_utf8_(GuUCS ucs, GuOut* out, GuExn* err)
 	}
 }
 
-extern inline GuUCS
-gu_in_utf8(GuIn* in, GuExn* err);
+extern inline void
+gu_out_utf8(GuUCS ucs, GuOut* out, GuExn* err);
+
+void
+gu_in_utf8_buf(uint8_t** buf, GuIn* in, GuExn* err)
+{
+	uint8_t* p = *buf;
+
+	uint8_t c = gu_in_u8(in, err);
+	if (!gu_ok(err)) {
+		return;
+	}
+	*(p++) = c;
+	int len = (c < 0x80 ? 0 : 
+		   c < 0xc2 ? -1 :
+		   c < 0xe0 ? 1 :
+		   c < 0xf0 ? 2 :
+		   c < 0xf5 ? 3 :
+		   -1);
+	if (len < 0) {
+	 	goto fail;
+	} else if (len == 0) {
+		*buf = p;
+		return;
+	}
+	static const uint8_t mask[4] = { 0x7f, 0x1f, 0x0f, 0x07 };
+	// If reading the extra bytes causes EOF, it is an encoding
+	// error, not a legitimate end of character stream.
+	GuExn* tmp_err = gu_exn(err, GuEOF, NULL);
+	gu_in_bytes(in, p, len, tmp_err);
+	if (tmp_err->caught) {
+		goto fail;
+	}
+	if (!gu_ok(err)) {
+		return;
+	}
+	*buf = p;
+	return;
+
+fail:
+	gu_raise(err, GuUCSExn);
+	return;
+}

src/runtime/c/gu/utf8.h

@@ -29,7 +29,12 @@ gu_out_utf8(GuUCS ucs, GuOut* out, GuExn* err)
 	}
 }
 
+// Helper functions used in other modules
+
 GuUCS
 gu_utf8_decode(const uint8_t** utf8);
 
+void
+gu_in_utf8_buf(uint8_t** buf, GuIn* in, GuExn* err);
+
 #endif // GU_UTF8_H_

src/runtime/c/pgf/reader.c

@@ -91,38 +91,15 @@ pgf_read_len(PgfReader* rdr)
 static PgfCId
 pgf_read_cid(PgfReader* rdr)
 {
-	GuPool* tmp_pool = gu_new_pool();
-	GuStringBuf* sbuf = gu_string_buf(tmp_pool);
-	GuOut* out = gu_string_buf_out(sbuf);
-
 	size_t len = pgf_read_len(rdr);
-	for (size_t i = 0; i < len; i++) {
-		// CIds are in latin-1
-		GuUCS ucs = gu_in_u8(rdr->in, rdr->err);
-		gu_out_utf8(ucs, out, rdr->err);
-	}
-	GuString str = gu_string_buf_freeze(sbuf, rdr->opool);
-	gu_pool_free(tmp_pool);
-	return str;
+	return gu_string_read_latin1(len, rdr->opool, rdr->in, rdr->err);
 }
 
 static GuString
 pgf_read_string(PgfReader* rdr)
 {	
-	GuPool* tmp_pool = gu_new_pool();
-	GuStringBuf* sbuf = gu_string_buf(tmp_pool);
-	GuOut* out = gu_string_buf_out(sbuf);
-
 	GuLength len = pgf_read_len(rdr);
-
-	for (size_t i = 0; i < len; i++) {
-		GuUCS ucs = gu_in_utf8(rdr->in, rdr->err);
-		gu_out_utf8(ucs, out, rdr->err);
-	}
-	GuString str = gu_string_buf_freeze(sbuf, rdr->opool);
-	gu_pool_free(tmp_pool);
-
-	return str;
+	return gu_string_read(len, rdr->opool, rdr->in, rdr->err);
 }
 
 static void