https://git.ruby-lang.org/ruby.git/commit/?id=51500eedef

From 51500eedefa492699668ced3e07e330a9a4d53ee Mon Sep 17 00:00:00 2001
From: Kenta Murata <mrkn@m...>
Date: Fri, 4 Dec 2020 15:50:13 +0900
Subject: memory_view.c: Add rb_memory_view_extract_item_members


diff --git a/ext/-test-/memory_view/memory_view.c b/ext/-test-/memory_view/memory_view.c
index f7c5090..621614b 100644
--- a/ext/-test-/memory_view/memory_view.c
+++ b/ext/-test-/memory_view/memory_view.c
@@ -80,15 +80,15 @@ memory_view_parse_item_format(VALUE mod, VALUE format) https://github.com/ruby/ruby/blob/trunk/ext/-test-/memory_view/memory_view.c#L80
     const char *err = NULL;
 
     rb_memory_view_item_component_t *members;
-    ssize_t n_members;
+    size_t n_members;
     ssize_t item_size = rb_memory_view_parse_item_format(c_str, &members, &n_members, &err);
 
     VALUE result = rb_ary_new_capa(3);
     rb_ary_push(result, SSIZET2NUM(item_size));
 
     if (!err) {
-        VALUE ary = rb_ary_new_capa(n_members);
-        ssize_t i;
+        VALUE ary = rb_ary_new_capa((long)n_members);
+        size_t i;
         for (i = 0; i < n_members; ++i) {
             VALUE member = rb_hash_new();
             rb_hash_aset(member, sym_format, rb_str_new(&members[i].format, 1));
@@ -231,6 +231,26 @@ memory_view_ref_count_while_exporting(VALUE mod, VALUE obj, VALUE n) https://github.com/ruby/ruby/blob/trunk/ext/-test-/memory_view/memory_view.c#L231
 }
 
 static VALUE
+memory_view_extract_item_members(VALUE mod, VALUE str, VALUE format)
+{
+    StringValue(str);
+    StringValue(format);
+
+    rb_memory_view_item_component_t *members;
+    size_t n_members;
+    const char *err = NULL;
+    (void)rb_memory_view_parse_item_format(RSTRING_PTR(format), &members, &n_members, &err);
+    if (err != NULL) {
+        rb_raise(rb_eArgError, "Unable to parse item format");
+    }
+
+    VALUE item = rb_memory_view_extract_item_members(RSTRING_PTR(str), members, n_members);
+    xfree(members);
+
+    return item;
+}
+
+static VALUE
 expstr_initialize(VALUE obj, VALUE s)
 {
     if (!NIL_P(s)) {
@@ -346,6 +366,7 @@ Init_memory_view(void) https://github.com/ruby/ruby/blob/trunk/ext/-test-/memory_view/memory_view.c#L366
     rb_define_module_function(mMemoryViewTestUtils, "get_memory_view_info", memory_view_get_memory_view_info, 1);
     rb_define_module_function(mMemoryViewTestUtils, "fill_contiguous_strides", memory_view_fill_contiguous_strides, 4);
     rb_define_module_function(mMemoryViewTestUtils, "ref_count_while_exporting", memory_view_ref_count_while_exporting, 2);
+    rb_define_module_function(mMemoryViewTestUtils, "extract_item_members", memory_view_extract_item_members, 2);
 
     VALUE cExportableString = rb_define_class_under(mMemoryViewTestUtils, "ExportableString", rb_cObject);
     rb_define_method(cExportableString, "initialize", expstr_initialize, 1);
diff --git a/include/ruby/memory_view.h b/include/ruby/memory_view.h
index e2c5cd9..7c8ed72 100644
--- a/include/ruby/memory_view.h
+++ b/include/ruby/memory_view.h
@@ -128,9 +128,10 @@ RBIMPL_ATTR_NOALIAS() https://github.com/ruby/ruby/blob/trunk/include/ruby/memory_view.h#L128
 int rb_memory_view_init_as_byte_array(rb_memory_view_t *view, VALUE obj, void *data, const ssize_t len, const bool readonly);
 ssize_t rb_memory_view_parse_item_format(const char *format,
                                          rb_memory_view_item_component_t **members,
-                                         ssize_t *n_members, const char **err);
+                                         size_t *n_members, const char **err);
 ssize_t rb_memory_view_item_size_from_format(const char *format, const char **err);
 void *rb_memory_view_get_item_pointer(rb_memory_view_t *view, const ssize_t *indices);
+VALUE rb_memory_view_extract_item_members(const void *ptr, const rb_memory_view_item_component_t *members, size_t n_members);
 
 int rb_memory_view_available_p(VALUE obj);
 int rb_memory_view_get(VALUE obj, rb_memory_view_t* memory_view, int flags);
diff --git a/memory_view.c b/memory_view.c
index 8b2a2c0..2bf3eee 100644
--- a/memory_view.c
+++ b/memory_view.c
@@ -12,6 +12,18 @@ https://github.com/ruby/ruby/blob/trunk/memory_view.c#L12
 #include "internal/util.h"
 #include "ruby/memory_view.h"
 
+#if SIZEOF_INTPTR_T == SIZEOF_LONG_LONG
+#   define INTPTR2NUM LL2NUM
+#   define UINTPTR2NUM ULL2NUM
+#elif SIZEOF_INTPTR_T == SIZEOF_LONG
+#   define INTPTR2NUM LONG2NUM
+#   define UINTPTR2NUM ULONG2NUM
+#else
+#   define INTPTR2NUM INT2NUM
+#   define UINTPTR2NUM UINT2NUM
+#endif
+
+
 #define STRUCT_ALIGNOF(T, result) do { \
     (result) = RUBY_ALIGNOF(T); \
 } while(0)
@@ -394,13 +406,13 @@ calculate_padding(ssize_t total, ssize_t alignment_size) { https://github.com/ruby/ruby/blob/trunk/memory_view.c#L406
 ssize_t
 rb_memory_view_parse_item_format(const char *format,
                                  rb_memory_view_item_component_t **members,
-                                 ssize_t *n_members, const char **err)
+                                 size_t *n_members, const char **err)
 {
     if (format == NULL) return 1;
 
     VALUE error = Qnil;
     ssize_t total = 0;
-    ssize_t len = 0;
+    size_t len = 0;
     bool alignment = false;
     ssize_t max_alignment_size = 0;
 
@@ -558,6 +570,215 @@ rb_memory_view_get_item_pointer(rb_memory_view_t *view, const ssize_t *indices) https://github.com/ruby/ruby/blob/trunk/memory_view.c#L570
     return ptr;
 }
 
+static void
+switch_endianness(uint8_t *buf, ssize_t len)
+{
+    RUBY_ASSERT(buf != NULL);
+    RUBY_ASSERT(len >= 0);
+
+    uint8_t *p = buf;
+    uint8_t *q = buf + len - 1;
+
+    while (q - p > 0) {
+        uint8_t t = *p;
+        *p = *q;
+        *q = t;
+        ++p;
+        --q;
+    }
+}
+
+static inline VALUE
+extract_item_member(const uint8_t *ptr, const rb_memory_view_item_component_t *member, const size_t i,
+                    uint8_t *buf, const size_t buf_size)
+{
+    RUBY_ASSERT(ptr != NULL);
+    RUBY_ASSERT(member != NULL);
+
+#ifdef WORDS_BIGENDIAN
+    const bool native_endian_p = !member->little_endian_p;
+#else
+    const bool native_endian_p = member->little_endian_p;
+#endif
+
+    const uint8_t *p = ptr + member->offset + i * member->size;
+
+    if (member->format == 'c') {
+        return INT2FIX(*(char *)p);
+    }
+    else if (member->format == 'C') {
+        return INT2FIX(*(unsigned char *)p);
+    }
+
+    const uint8_t *q = p;
+
+    if (!native_endian_p) {
+        RUBY_ASSERT(buf != NULL);
+        MEMCPY(buf, p, uint8_t, member->size);
+        switch_endianness(buf, member->size);
+        q = buf;
+    }
+
+    switch (member->format) {
+      case 's':
+        if (member->native_size_p) {
+            return INT2FIX(*(short *)q);
+        }
+        else {
+            return INT2FIX(*(int16_t *)q);
+        }
+
+      case 'S':
+      case 'n':
+      case 'v':
+        if (member->native_size_p) {
+            return UINT2NUM(*(unsigned short *)q);
+        }
+        else {
+            return INT2FIX(*(uint16_t *)q);
+        }
+
+      case 'i':
+        return INT2NUM(*(int *)q);
+
+      case 'I':
+        return UINT2NUM(*(unsigned int *)q);
+
+      case 'l':
+        if (member->native_size_p) {
+            return LONG2NUM(*(long *)q);
+        }
+        else {
+            return LONG2NUM(*(int32_t *)q);
+        }
+
+      case 'L':
+      case 'N':
+      case 'V':
+        if (member->native_size_p) {
+            return ULONG2NUM(*(unsigned long *)q);
+        }
+        else {
+            return ULONG2NUM(*(uint32_t *)q);
+        }
+
+      case 'f':
+      case 'e':
+      case 'g':
+        return DBL2NUM(*(float *)q);
+
+      case 'q':
+        if (member->native_size_p) {
+            return LL2NUM(*(LONG_LONG *)q);
+        }
+        else {
+#if SIZEOF_INT64_t == SIZEOF_LONG
+            return LONG2NUM(*(int64_t *)q);
+#else
+            return LL2NUM(*(int64_t *)q);
+#endif
+        }
+
+      case 'Q':
+        if (member->native_size_p) {
+            return ULL2NUM(*(unsigned LONG_LONG *)q);
+        }
+        else {
+#if SIZEOF_UINT64_t == SIZEOF_LONG
+            return ULONG2NUM(*(uint64_t *)q);
+#else
+            return ULL2NUM(*(uint64_t *)q);
+#endif
+        }
+
+      case 'd':
+      case 'E':
+      case 'G':
+        return DBL2NUM(*(double *)q);
+
+      case 'j':
+        return INTPTR2NUM(*(intptr_t *)q);
+
+      case 'J':
+        return UINTPTR2NUM(*(uintptr_t *)q);
+
+      default:
+        UNREACHABLE_RETURN(Qnil);
+    }
+}
+
+/* Return a value of the extracted member. */
+VALUE
+rb_memory_view_extract_item_member(const void *ptr, const rb_memory_view_item_component_t *member, const size_t i)
+{
+    if (ptr == NULL) return Qnil;
+    if (member == NULL) return Qnil;
+    if (i >= member->repeat) return Qnil;
+
+#ifdef WORDS_BIGENDIAN
+    const bool native_endian_p = !member->little_endian_p;
+#else
+    const bool native_endian_p = member->little_endian_p;
+#endif
+
+    VALUE buf_v = 0;
+    uint8_t *buf;
+    if (!native_endian_p) {
+        buf = ALLOCV_N(uint8_t, buf_v, member->size);
+    }
+
+    VALUE v = extract_item_member(ptr, member, i, buf, member->size);
+
+    if (buf_v) ALLOCV_END(buf_v);
+    return v;
+}
+
+/* Return a value that consists of item members.
+ * When an item is a single member, the return value is a single value.
+ * When an item consists of multiple members, an array will be returned. */
+VALUE
+rb_memory_view_extract_item_members(const void *ptr, const rb_memory_view_item_component_t *members, const size_t n_members)
+{
+    if (ptr == NULL) return Qnil;
+    if (members == NULL) return Qnil;
+    if (n_members == 0) return Qnil;
+
+    if (n_members == 1 && members[0].repeat == 1) {
+        return rb_memory_view_extract_item_member(ptr, members, 0);
+    }
+
+    size_t i, max_size = 0;
+    bool need_switch_endianness_p = false;
+    for (i = 0; i < n_members; ++i) {
+        if (max_size < members[i].size) {
+            max_size = members[i].size;
+        }
+#ifdef WORDS_BIGE (... truncated)

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