From ac7ec87484894c040681e7d59c6b12a966a23f7b Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Mon, 14 Mar 2022 17:00:10 +0000
Subject: [PATCH] Start: string_view for C
MIME-Version: 1.0
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Fortune for sink's current commit: Small curse − 小凶
---
 Makefile |  2 +-
 view.c   | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 view.h   | 22 ++++++++++++++
 3 files changed, 112 insertions(+), 1 deletion(-)
 create mode 100644 view.c
 create mode 100644 view.h

diff --git a/Makefile b/Makefile
index bf580dc..2e3dc7b 100644
--- a/Makefile
+++ b/Makefile
@@ -52,7 +52,7 @@ RELEASE_LDFLAGS+= -Wl,-O3 -Wl,-flto
 DEBUG_CFLAGS+=-Og -g3 -ggdb -gz -DDEBUG
 DEBUG_LDFLASG+=-Wl,-g
 
-CFLAGS   += $(COMMON_FLAGS) --std=gnu17
+CFLAGS   += $(COMMON_FLAGS) --std=gnu2x
 LDFLAGS  +=
 
 ifneq ($(SHARED),yes)
diff --git a/view.c b/view.c
new file mode 100644
index 0000000..b96a9bf
--- /dev/null
+++ b/view.c
@@ -0,0 +1,89 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdbool.h>
+
+#include "view.h"
+
+#define S_PTR_MASK (0xcafebeef00000000ul) /* XXX: Should this frob the high or end parts of the pointer? We'll go with high? */
+
+#define $mixin __attribute__((__gnu_inline__, __always_inline__, __artificial__)) inline
+#define $nullchk(ptr, or) ({ __auto_type _$p = (ptr); \
+			__builtin_expect(_$p == NULL, false) ? ({ or; }),NULL : _$p; })
+
+typedef uint8_t byte_t;
+
+__attribute__((packed))
+struct string_metadata {
+	bool is_owned	: 1; // was the string malloc()'d
+	bool has_nul	: 1; // does this string have a nul terminator
+};
+
+struct string_data {
+	struct string_metadata meta;
+
+	uintptr_t ptr_frob;
+
+	
+	struct /*_Alignas(struct string_view)*/ {
+		size_t len;
+		char ptr[];
+	} __attribute__((aligned(_Alignof(struct string_view)))); //__attribute__((align(struct string_view)));
+};
+
+#define _s_frob_pointer_(p, f) ((/*__typeof((p))*/void*) (((uintptr_t)(p)) ^ ((uintptr_t)(f))))
+__attribute__((const))
+$mixin static void* _s_frob_pointer(void* p) 
+{
+	return _s_frob_pointer_(p, S_PTR_MASK); 
+}
+#define _s_frob_pointer(p) _s_frob_pointer_((p), S_PTR_MASK)
+
+#define $frob(v, w) _s_frob_pointer_((v), (w))
+
+static inline struct string* _s_frob(struct string_data* restrict d) {
+	return (struct string*) _s_frob_pointer(d->ptr);
+}
+static inline struct string_data* _s_unfrob(struct string *restrict ptr) { 
+//	static const off64_t O_this = offsetof(struct string_data, ptr);
+
+	struct string_data* restrict base = (void*)((byte_t*)_s_frob_pointer(ptr)) - offsetof(struct string_data, ptr);
+
+	uintptr_t frob = base->ptr_frob;
+	if(frob != ((uintptr_t)_s_frob_pointer(base))) return NULL; //XXX: TODO: Is this valid? Probably, since struct string_data will only ever be heap-allocated.
+
+	return base;
+}
+
+$mixin static char* _s_str(struct string_data* restrict data) { return data->ptr; }
+
+$mixin extern struct string_data* _s_data(char* str, bool check) {
+	struct string_data* sd = (struct string_data*)( ((byte_t*)str) - offsetof(struct string_data, ptr) );
+
+	if(__builtin_constant_p(check) && !check) return sd;
+	else if(check && sd->ptr_frob != ((uintptr_t)_s_frob_pointer(sd))) return NULL; 
+	else return sd;
+}
+static struct string_data* _s_data(char* str, bool check) {
+	static const size_t O_base = offsetof(struct string_data, ptr);
+	struct string_data* sd = (struct string_data*)( ((byte_t*)str) - O_base );
+
+	if(__builtin_constant_p(check) && !check) return sd;
+	else if(check && sd->ptr_frob != ((uintptr_t)_s_frob_pointer(sd))) return NULL;
+	else return sd;
+}
+
+__attribute__((pure))
+str_info_t s_get_info(sv_t str) 
+{
+	return _s_data($nullchk(str.ptr, return NULL), true);
+}
+
+__attribute__((pure))
+sv_t s_get_str(str_info_t data) 
+{ 
+	return (sv_t) {
+		.len = data->len,
+		.ptr = (unsigned char*)data->ptr,
+	};
+}
diff --git a/view.h b/view.h
new file mode 100644
index 0000000..78191c0
--- /dev/null
+++ b/view.h
@@ -0,0 +1,22 @@
+#ifndef _VIEW_H
+#define _VIEW_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+typedef struct string_view {
+	size_t len;
+	unsigned char* ptr;
+} sv_t;
+
+struct string_data;
+typedef struct string_data* str_info_t;
+
+struct string;
+
+// Functions //
+
+sv_t s_get_str(str_info_t data) __attribute__((pure));
+str_info_t s_get_info(sv_t str) __attribute__((pure));
+
+#endif /* _VIEW_H */