From 10f2042bee77c057cbfe19492ab83ed41a9f1f27 Mon Sep 17 00:00:00 2001
From: Tau <tau@nowhere>
Date: Sun, 23 May 2021 11:39:33 -0400
Subject: [PATCH] Add DLL binding helper

---
 util/dll-bind.c  | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 util/dll-bind.h  | 33 +++++++++++++++++++++++++++++++++
 util/meson.build |  2 ++
 3 files changed, 82 insertions(+)
 create mode 100644 util/dll-bind.c
 create mode 100644 util/dll-bind.h

diff --git a/util/dll-bind.c b/util/dll-bind.c
new file mode 100644
index 0000000..9568d33
--- /dev/null
+++ b/util/dll-bind.c
@@ -0,0 +1,47 @@
+#include <windows.h>
+
+#include <assert.h>
+#include <stdint.h>
+
+#include "util/dll-bind.h"
+#include "util/dprintf.h"
+
+HRESULT dll_bind(
+    void *dest,
+    HINSTANCE src,
+    const struct dll_bind_sym **syms_pos,
+    size_t syms_count)
+{
+    HRESULT hr;
+    void *src_result;
+    void **dest_field;
+    const struct dll_bind_sym *current_sym;
+    size_t i;
+
+    assert(dest != NULL);
+    assert(src != NULL);
+    assert(syms_pos != NULL);
+
+    hr = S_OK;
+    current_sym = *syms_pos;
+
+    assert(current_sym != NULL);
+
+    for (i = 0; i < syms_count; i++) {
+        src_result = GetProcAddress(src, current_sym->sym);
+
+        if (src_result == NULL) {
+            hr = E_NOTIMPL;
+
+            break;
+        }
+
+        dest_field = (void **)(((uint8_t *)dest) + current_sym->off);
+        *dest_field = src_result;
+        current_sym++;
+    }
+
+    *syms_pos = current_sym;
+
+    return hr;
+}
diff --git a/util/dll-bind.h b/util/dll-bind.h
new file mode 100644
index 0000000..08e647b
--- /dev/null
+++ b/util/dll-bind.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <windows.h>
+
+#include <stdlib.h>
+
+struct dll_bind_sym {
+    /* Symbol name to locate in the source DLL */
+    const char *sym;
+
+    /* Offset where the symbol pointer should be written in the target
+       structure */
+    ptrdiff_t off;
+};
+
+/*
+    Bind a list of DLL symbols into a structure that contains function
+    pointers.
+
+    - dest: Pointer to destination structure.
+    - src: Handle to source DLL.
+    - syms_pos: Pointer to a (mutable) pointer which points to the start of an
+        (immutable) table of symbols and structure offsets. This mutable
+        pointer is advanced until either a symbol fails to bind, in which case
+        an error is returned, or the end of the table is reached, in which
+        case success is returned.
+   - syms_count: Number of entries in the symbol table.
+*/
+HRESULT dll_bind(
+        void *dest,
+        HINSTANCE src,
+        const struct dll_bind_sym **syms_pos,
+        size_t syms_count);
diff --git a/util/meson.build b/util/meson.build
index 0b76284..c3c07f9 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -11,6 +11,8 @@ util_lib = static_library(
         'async.h',
         'crc.c',
         'crc.h',
+        'dll-bind.c',
+        'dll-bind.h',
         'dprintf.c',
         'dprintf.h',
         'dump.c',