From d7ddeaf2cab0737cc7bd70a29af771a7ba75ac4d Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Mon, 12 Jul 2021 23:51:45 +0100
Subject: [PATCH] Use `slice_sted()` on base-removed slice to calculate offsets
 instead of using ad-hoc anonymous struct in-line.
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I don"t know if this is more efficient or not, but it looks cleaner. Define `_DEBUG_MANCALC_OFFSETS` to use the previous offset calculation code.

Fortune for naka's current commit: Small blessing − 小吉
---
 include/slice.h   | 36 ++++++++++++++++++++++++++++++++++++
 src/main.c        |  6 ++++++
 src/slice.c       | 37 +++++++++++++++++++++++++++++++++++++
 src/tests/slice.c | 19 +++++++++++++++++++
 4 files changed, 98 insertions(+)
 create mode 100644 src/slice.c
 create mode 100644 src/tests/slice.c

diff --git a/include/slice.h b/include/slice.h
index 0a900d4..5bea5a6 100644
--- a/include/slice.h
+++ b/include/slice.h
@@ -2,7 +2,10 @@
 #ifndef _SLICE_H
 #define _SLICE_H
 
+#include <limits.h>
+
 #include "ints.h"
+#include "macros.h"
 
 typedef struct _slice {
 	union {
@@ -12,6 +15,39 @@ typedef struct _slice {
 	usize len;
 } slice_t;
 
+#define SLICE_MAX ((struct _slice){ .ptr = AS(UINTPTR_MAX, void*), .len = SIZE_MAX })
+
 #define SLICE(origin, length) ((struct _slice){ .ptr = ((void*)(origin)), .len = ((usize)(length)) })
 
+_mixin usize slice_end(const slice_t*pIN slice)
+{
+	return AS(slice->bytes + slice->len, usize);
+}
+
+_mixin usize slice_start(const slice_t*pIN slice)
+{
+	return AS(slice->bytes, usize);
+}
+
+_mixin struct { usize start, end; } slice_sted(const slice_t*pIN slice)
+{
+	return (var(slice_sted(NULL))){
+		.start = slice_start(slice),
+		.end = slice_end(slice),
+	};
+}
+
+// Format string for slices
+#define SLICE_FORMAT "%lu..%lu"
+// Expects a pointer to a `slice_t`
+#define SLICE_FORMAT_ARGS(slice) slice_start(slice), slice_end(slice)
+
+#define SLICE_STR_MAX_SIZE 42lu
+usize slice_strn(const slice_t*pIN slice, usize len, char str[static pOUT len]);
+usize slice_str_sz(const slice_t*pIN slice);
+// Pointer returned from this function is TLS static and will change on each call.
+const char* slice_strs(const slice_t*pIN slice);
+// Pointer returned from this function must be free'd
+char* slice_str(const slice_t*pIN slice);
+
 #endif /* _SLICE_H */
diff --git a/src/main.c b/src/main.c
index 0426b2b..0775c82 100644
--- a/src/main.c
+++ b/src/main.c
@@ -13,6 +13,7 @@
 
 #include <tests.h>
 
+#include <slice.h>
 #include <map.h>
 #include <comp.h>
 
@@ -179,12 +180,17 @@ inv_args:
 		if(!comp_slice_of(&needle, current++, &cslice)) {
 			printf("fail: %lu\n", i+1);
 		} else {
+#ifdef _DEBUG_MANCALC_OFFSETS
 			struct {
 				usize start, end;
 			} pos = {
 				.start = AS(cslice.ptr - base, usize),
 			};
 			pos.end = pos.start + cslice.len;
+#else
+			let pos = slice_sted((slice_t[]){ SLICE(AS(cslice.ptr - base, usize), cslice.len)});
+#endif
+			INFO("Mapped region slice for %lu, pre-transform (at %p): " SLICE_FORMAT ", len: %lu", i+1, base, SLICE_FORMAT_ARGS(&cslice), cslice.len);
 			printf("match: %lu: %lu -> %lu\n", i+1, pos.start, pos.end);
 		}
 	}
diff --git a/src/slice.c b/src/slice.c
new file mode 100644
index 0000000..5e7bcb7
--- /dev/null
+++ b/src/slice.c
@@ -0,0 +1,37 @@
+#include <stdio.h>
+
+#include <slice.h>
+
+usize slice_strn(const slice_t*pIN slice, usize len, char str[static pOUT len])
+{
+	return snprintf(str, len, SLICE_FORMAT, SLICE_FORMAT_ARGS(slice));
+}
+
+usize slice_str_sz(const slice_t*pIN slice)
+{
+	return snprintf(NULL, 0, SLICE_FORMAT, SLICE_FORMAT_ARGS(slice)); 
+}
+
+usize _slice_str_max_sz()
+{
+	const slice_t max = SLICE_MAX;
+	return snprintf(NULL, 0, SLICE_FORMAT, SLICE_FORMAT_ARGS(&max)); 
+}
+
+const char* slice_strs(const slice_t*pIN slice)
+{
+	static _Thread_local char buf[SLICE_STR_MAX_SIZE+1];
+	debug_assert(sizeof(buf) == SLICE_STR_MAX_SIZE+1);
+	buf[snprintf(buf, sizeof(buf), SLICE_FORMAT, SLICE_FORMAT_ARGS(slice))] = 0;
+	return buf;
+}
+
+char* slice_str(const slice_t*pIN slice)
+{
+	usize ln = slice_str_sz(slice)+1;
+	char *buf = malloc(ln);
+	usize _out = slice_strn(slice, ln, buf);
+	debug_assert(_out == ln);
+	IGNORE(_out);
+	return buf;
+}
diff --git a/src/tests/slice.c b/src/tests/slice.c
new file mode 100644
index 0000000..da1e94e
--- /dev/null
+++ b/src/tests/slice.c
@@ -0,0 +1,19 @@
+
+#include <macros.h>
+#include <tests.h>
+
+#include <slice.h>
+
+// Internal `slice.c` function prototyped.
+usize _slice_str_max_sz();
+
+DEFTEST(slice_static_str_len)
+{
+	const usize func = _slice_str_max_sz();
+	INFO("Function reports: %lu", func);
+	INFO("Constant is: %lu", SLICE_STR_MAX_SIZE);
+	TEST_ASSERT( (func == SLICE_STR_MAX_SIZE) );
+
+	return TEST_OK;
+}
+RUNTEST_DEBUG(slice_static_str_len)