commit f0383c92942287433ee06f314b50593a13663077
Author: Stanislav N Mikhailov <stas@enso.pro>
Date:   Mon Mar 9 18:35:43 2026 +0300

    Initial SHA256 test harness

diff --git a/.gitignore b/.gitignore
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--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+build/*
+!build/Debug/
+build/Debug/*
+!build/Debug/*.exe
+!build/Debug/*.dll
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..bb8a657
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.20)
+project(sha256_client_c LANGUAGES C)
+
+if(NOT WIN32)
+    message(FATAL_ERROR "This sample is intended for Win64 (DLL import).")
+endif()
+
+add_executable(sha256_client
+    src/main.c
+)
+
+target_include_directories(sha256_client PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/include
+)
+
+target_link_libraries(sha256_client PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/dll/sha-256.lib
+)
+
+add_custom_command(TARGET sha256_client POST_BUILD
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different
+            ${CMAKE_CURRENT_SOURCE_DIR}/dll/sha-256.dll
+            $<TARGET_FILE_DIR:sha256_client>/sha-256.dll
+)
diff --git a/build/Debug/sha-256.dll b/build/Debug/sha-256.dll
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Binary files /dev/null and b/build/Debug/sha-256.dll differ
diff --git a/build/Debug/sha256_client.exe b/build/Debug/sha256_client.exe
new file mode 100644
index 0000000..834c41c
Binary files /dev/null and b/build/Debug/sha256_client.exe differ
diff --git a/dll/sha-256.dll b/dll/sha-256.dll
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index 0000000..a4863bc
Binary files /dev/null and b/dll/sha-256.dll differ
diff --git a/dll/sha-256.lib b/dll/sha-256.lib
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index 0000000..d66ca90
Binary files /dev/null and b/dll/sha-256.lib differ
diff --git a/include/sha.h b/include/sha.h
new file mode 100644
index 0000000..dbe8084
--- /dev/null
+++ b/include/sha.h
@@ -0,0 +1,48 @@
+#ifndef SHA256_SHA_H
+#define SHA256_SHA_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef _WIN32
+  #ifdef SHA256_EXPORTS
+    #define SHA256_API __declspec(dllexport)
+  #else
+    #define SHA256_API __declspec(dllimport)
+  #endif
+#else
+  #define SHA256_API
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef uint32_t sha256_digest_t[8];
+
+SHA256_API int TestHello(void);
+
+/*
+ * Returns NULL (0) on success according to assembly comments.
+ * data_addr      - pointer to current data chunk.
+ * full_size      - total message/file size in bytes.
+ * current_size   - current chunk size in bytes.
+ * digest         - 32-byte state/result buffer (8 x uint32_t).
+ * is_last_chunk  - 1 if this is the last chunk, otherwise 0.
+ */
+SHA256_API void *Sha256(
+    const void *data_addr,
+    uint64_t full_size,
+    uint64_t current_size,
+    sha256_digest_t digest,
+    uint64_t is_last_chunk
+);
+
+/* Initializes digest and internal K constants. */
+SHA256_API void Sha256Init(sha256_digest_t digest);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SHA256_SHA_H */
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..d116190
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,95 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "sha.h"
+
+static void print_digest_words(const sha256_digest_t digest) {
+    for (int i = 0; i < 8; ++i) {
+        printf("%08x", digest[i]);
+    }
+    putchar('\n');
+}
+
+int main(void) {
+    char path[4096] = {0};
+    sha256_digest_t digest = {0};
+
+    if (fgets(path, (int)sizeof(path), stdin) == NULL) {
+        fprintf(stderr, "Failed to read file path from stdin\n");
+        return 1;
+    }
+
+    path[strcspn(path, "\r\n")] = '\0';
+    if (path[0] == '\0') {
+        fprintf(stderr, "Empty file path\n");
+        return 1;
+    }
+
+    FILE *fp = fopen(path, "rb");
+    if (fp == NULL) {
+        fprintf(stderr, "Failed to open file: %s\n", path);
+        return 1;
+    }
+
+    if (_fseeki64(fp, 0, SEEK_END) != 0) {
+        fprintf(stderr, "Failed to seek file end: %s\n", path);
+        fclose(fp);
+        return 1;
+    }
+
+    const long long file_size_ll = _ftelli64(fp);
+    if (file_size_ll < 0) {
+        fprintf(stderr, "Failed to get file size: %s\n", path);
+        fclose(fp);
+        return 1;
+    }
+
+    if (_fseeki64(fp, 0, SEEK_SET) != 0) {
+        fprintf(stderr, "Failed to seek file start: %s\n", path);
+        fclose(fp);
+        return 1;
+    }
+
+    const uint64_t full_size = (uint64_t)file_size_ll;
+    size_t alloc_size = (size_t)full_size;
+    if ((uint64_t)alloc_size != full_size) {
+        fprintf(stderr, "File is too large for this client: %s\n", path);
+        fclose(fp);
+        return 1;
+    }
+    if (alloc_size == 0) { 
+        alloc_size = 1;
+    }
+
+    unsigned char *data = (unsigned char *)malloc(alloc_size);
+    if (data == NULL) {
+        fprintf(stderr, "Out of memory while reading: %s\n", path);
+        fclose(fp);
+        return 1;
+    }
+
+    if (full_size > 0) {
+        const size_t read_size = fread(data, 1, (size_t)full_size, fp);
+        if (read_size != (size_t)full_size) {
+            fprintf(stderr, "Failed to read file: %s\n", path);
+            free(data);
+            fclose(fp);
+            return 1;
+        }
+    }
+    fclose(fp);
+
+    void *rc = Sha256(data, full_size, full_size, digest, 1);
+    free(data);
+    if (rc != 0) {
+        fprintf(stderr, "Sha256 failed, rc=%p\n", rc);
+        return 1;
+    }
+
+    printf("Digest (library word order): ");
+    print_digest_words(digest);
+
+    return 0;
+}