From acce76aa4c87017f3b668a07011ff55fbca411f3 Mon Sep 17 00:00:00 2001
From: Nikita Smith <git.nikita.smith@gmail.com>
Date: Fri, 27 Mar 2026 11:13:10 -0700
Subject: [PATCH] string list sub range helper

---
 src/base/base_strings.c    | 36 +++++++++++++++++++
 src/base/base_strings.h    |  1 +
 src/torture/torture.h      | 30 ++++++++--------
 src/torture/torture_base.c | 73 ++++++++++++++++++++++++++++++++++++++
 src/torture/torture_main.c |  1 +
 5 files changed, 126 insertions(+), 15 deletions(-)
 create mode 100644 src/torture/torture_base.c

diff --git a/src/base/base_strings.c b/src/base/base_strings.c
index 9d489476..57c908fd 100644
--- a/src/base/base_strings.c
+++ b/src/base/base_strings.c
@@ -1143,6 +1143,42 @@ str8_list_copy(Arena *arena, String8List *list)
   return result;
 }
 
+internal String8List
+str8_list_substr(Arena *arena, String8List list, Rng1U64 range)
+{
+  String8List result = {0};
+
+  String8Node *n = list.first;
+
+  U64 front_min = 0;
+  {
+    U64 cursor = 0;
+    for (; n != 0; cursor += n->string.size, n = n->next) {
+      if (cursor + n->string.size > range.min) {
+        front_min = range.min - cursor;
+        break;
+      }
+    }
+  }
+
+  if (front_min > 0) {
+    U64 front_max = front_min + Min(dim_1u64(range), n->string.size);
+    str8_list_push(arena, &result, str8_substr(n->string, r1u64(front_max, front_max)));
+    n = n->next;
+  }
+
+  for (; n != 0; n = n->next) {
+    if (result.total_size >= dim_1u64(range)) {
+      break;
+    }
+    U64 copy_max  = dim_1u64(range) - result.total_size;
+    U64 copy_size = Min(copy_max, n->string.size);
+    str8_list_push(arena, &result, str8_substr(n->string, r1u64(0, copy_size)));
+  }
+
+  return result;
+}
+
 ////////////////////////////////
 //~ rjf: String Splitting & Joining
 
diff --git a/src/base/base_strings.h b/src/base/base_strings.h
index 635bc9ee..e86c4dee 100644
--- a/src/base/base_strings.h
+++ b/src/base/base_strings.h
@@ -269,6 +269,7 @@ internal String8Node* str8_list_pushf(Arena *arena, String8List *list, char *fmt
 internal String8Node* str8_list_push_frontf(Arena *arena, String8List *list, char *fmt, ...);
 internal String8Node* str8_list_pop_front(String8List *list);
 internal String8List  str8_list_copy(Arena *arena, String8List *list);
+internal String8List  str8_list_substr(Arena *arena, String8List list, Rng1U64 range);
 #define str8_list_first(list) ((list)->first ? (list)->first->string : str8_zero())
 
 ////////////////////////////////
diff --git a/src/torture/torture.h b/src/torture/torture.h
index a2e90725..7a1638f6 100644
--- a/src/torture/torture.h
+++ b/src/torture/torture.h
@@ -39,10 +39,10 @@ typedef struct
 extern U64    g_torture_test_count;
 extern T_Test g_torture_tests[0xffffff];
 
-#define T_AddTest(name, l, ...)                                      \
-T_RunResult t_##name(void);                                        \
-__VA_ARGS__ void t_add_test_##name(void)                           \
-{                                                                  \
+#define T_AddTest(name, l, ...)                                \
+T_RunResult t_##name(void);                                    \
+__VA_ARGS__ void t_add_test_##name(void)                       \
+{                                                              \
 g_torture_tests[g_torture_test_count].group = T_Group;         \
 g_torture_tests[g_torture_test_count].label = Stringify(name); \
 g_torture_tests[g_torture_test_count].r     = &t_##name;       \
@@ -52,7 +52,7 @@ g_torture_test_count += 1;                                     \
 
 #if COMPILER_MSVC
 #pragma section(".CRT$XCU", read)
-# define T_BeginTest_(name)                                                     \
+# define T_BeginTest_(name)                                                 \
 T_AddTest(name, __LINE__)                                                   \
 __declspec(allocate(".CRT$XCU")) void(*r_##name)(void) = t_add_test_##name; \
 __pragma(comment(linker, "/include:" Stringify(r_##name)))
@@ -61,20 +61,20 @@ __pragma(comment(linker, "/include:" Stringify(r_##name)))
 T_AddTest(name, __LINE__, __attribute__((constructor)))
 #endif
 
-#define T_BeginTest(name)                       \
-T_BeginTest_(name)                            \
-T_RunResult t_##name(void) {                  \
+#define T_BeginTest(name)                 \
+T_BeginTest_(name)                        \
+T_RunResult t_##name(void) {              \
 Temp        scratch = scratch_begin(0,0); \
-T_RunResult result  = { .status = T_RunStatus_Fail };
+T_RunResult result_ = { .status = T_RunStatus_Fail };
 
-#define T_EndTest                     \
-result.status = T_RunStatus_Pass; \
-exit__:;                          \
-scratch_end(scratch);             \
-return result;                    \
+#define T_EndTest                  \
+result_.status = T_RunStatus_Pass; \
+exit__:;                           \
+scratch_end(scratch);              \
+return result_;                    \
 }
 
-#define T_Ok(c) do { if (!(c)) { result.fail_file = __FILE__; result.fail_line = __LINE__; result.fail_cond = Stringify(c); goto exit__; } } while(0)
+#define T_Ok(c) do { if (!(c)) { result_.fail_file = __FILE__; result_.fail_line = __LINE__; result_.fail_cond = Stringify(c); goto exit__; } } while(0)
 #define T_MatchLinef(out, ...) T_Ok(t_match_linef(out, __VA_ARGS__))
 
 ////////////////////////////////
diff --git a/src/torture/torture_base.c b/src/torture/torture_base.c
new file mode 100644
index 00000000..724820ed
--- /dev/null
+++ b/src/torture/torture_base.c
@@ -0,0 +1,73 @@
+// Copyright (c) Epic Games Tools
+// Licensed under the MIT license (https://opensource.org/license/mit/)
+
+#define T_Group "Base"
+
+T_BeginTest(str8_list_substr)
+{
+  String8List zero_list = {0};
+
+  {
+    String8List list = {0};
+    str8_list_pushf(scratch.arena, &list, "a");
+    str8_list_pushf(scratch.arena, &list, "b");
+    str8_list_pushf(scratch.arena, &list, "c");
+    String8List sub = str8_list_substr(scratch.arena, list, r1u64(0, 3));
+    String8 result = str8_list_join(scratch.arena, &list, 0);
+    T_Ok(str8_match(result, str8_lit("abc"), 0));
+  }
+
+  {
+    String8List list = {0};
+    str8_list_pushf(scratch.arena, &list, "a");
+    str8_list_pushf(scratch.arena, &list, "b");
+    str8_list_pushf(scratch.arena, &list, "c");
+    String8List sub = str8_list_substr(scratch.arena, list, r1u64(0, max_U64));
+    String8 result = str8_list_join(scratch.arena, &list, 0);
+    T_Ok(str8_match(result, str8_lit("abc"), 0));
+  }
+
+  {
+
+    String8List list = {0};
+    str8_list_pushf(scratch.arena, &list, "a");
+    str8_list_pushf(scratch.arena, &list, "bcd");
+    String8List sub = str8_list_substr(scratch.arena, list, r1u64(2, 3));
+    String8 result = str8_list_join(scratch.arena, &sub, 0);
+    T_Ok(str8_match(result, str8_lit("c"), 0));
+  }
+
+  {
+
+    String8List list = {0};
+    str8_list_pushf(scratch.arena, &list, "a");
+    str8_list_pushf(scratch.arena, &list, "bcd");
+    String8List sub = str8_list_substr(scratch.arena, list, r1u64(1, 2));
+    String8 result = str8_list_join(scratch.arena, &sub, 0);
+    T_Ok(str8_match(result, str8_lit("b"), 0));
+  }
+
+  {
+    String8List list = {0};
+    str8_list_pushf(scratch.arena, &list, "ab");
+    str8_list_pushf(scratch.arena, &list, "cd");
+    str8_list_pushf(scratch.arena, &list, "ef");
+    String8List sub = str8_list_substr(scratch.arena, list, r1u64(1, 5));
+    String8 result = str8_list_join(scratch.arena, &sub, 0);
+    T_Ok(str8_match(result, str8_lit("bcde"), 0));
+  }
+
+  {
+    String8List list = {0};
+    str8_list_pushf(scratch.arena, &list, "abc");
+
+    String8List zero = str8_list_substr(scratch.arena, list, r1u64(0, 0));
+    T_Ok(MemoryMatchStruct(&zero, &zero_list));
+
+    String8List out_of_bounds_range = str8_list_substr(scratch.arena, list, r1u64(max_U64/2, max_U64));
+    T_Ok(MemoryMatchStruct(&out_of_bounds_range, &zero_list));
+  }
+}
+T_EndTest;
+
+#undef T_Group
diff --git a/src/torture/torture_main.c b/src/torture/torture_main.c
index fec9f504..3fab8992 100644
--- a/src/torture/torture_main.c
+++ b/src/torture/torture_main.c
@@ -72,6 +72,7 @@
 #include "linker/thread_pool/thread_pool.c"
 #include "linker/codeview_ext/codeview.c"
 #include "torture.c"
+#include "torture_base.c"
 #include "torture_radlink.c"
 #include "torture_dwarf.c"
 #include "torture_d2r.c"