From 9282991429a92d6df17213acdc49fe687f42da6c Mon Sep 17 00:00:00 2001
From: Jack Jamison <jackqjamison@gmail.com>
Date: Thu, 23 Jul 2026 15:34:43 -0400
Subject: download db is now source db, ready to start build

---
 snag/src/source_db.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 snag/src/source_db.c

(limited to 'snag/src/source_db.c')

diff --git a/snag/src/source_db.c b/snag/src/source_db.c
new file mode 100644
index 0000000..ab7ec99
--- /dev/null
+++ b/snag/src/source_db.c
@@ -0,0 +1,123 @@
+#include "source_db.h"
+
+#include "util.h"
+
+#include <curl/curl.h>
+#include <openssl/evp.h>
+#include <openssl/sha.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+// libcrpyto context
+EVP_MD_CTX *mdctx = NULL;
+const EVP_MD *md = NULL;
+void ensure_libcrypto();
+
+// curl context
+CURL *curl = NULL;
+void ensure_libcurl();
+
+// note: fixed location of source database for now
+const char source_db_path[] = "./var/snag/sources";
+char* get_source_path(source_info_t* source) { return join_path(source_db_path, source->name); }
+
+bool verify_source(source_info_t* source) {
+	// verify source exists
+	char* source_path = get_source_path(source);
+	bool verified = access(source_path, F_OK) == 0;
+
+	// todo(jqj): actually verify checksum
+	free(source_path);
+	return verified;
+}
+
+static size_t download_write_callback(char* ptr, size_t size, size_t nmemb, void* usrdata);
+bool download_source(source_info_t* source) {
+
+	char* source_path = get_source_path(source);
+	print("Downloading %s\n", source->url);
+
+	// initialize libcurl and libcrypto if they aren't already
+	ensure_libcurl();
+	ensure_libcrypto();
+
+	// initialize sha256 hash
+    EVP_DigestInit_ex(mdctx, md, NULL);
+
+	// open file for writing
+	FILE* download_file = fopen(source_path, "wb");
+	if (download_file == NULL) die("failed open download file for writing (%s): %s", source_path, strerror(errno));
+
+	// make curl request with url and output file
+	// callback writes to the file and feeds the hash
+	curl_easy_setopt(curl, CURLOPT_WRITEDATA, download_file);
+	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, download_write_callback);
+	curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
+	curl_easy_setopt(curl, CURLOPT_URL, source->url);
+	CURLcode result = curl_easy_perform(curl);
+	fclose(download_file);
+    if(result != CURLE_OK) {
+		// todo(jqj): handle better, maybe try again
+		print("failed to download package with curl: %s", curl_easy_strerror(result));
+		goto fail;
+	}
+
+	// get sha256 hash
+    unsigned char hash[SHA256_DIGEST_LENGTH];
+	unsigned int hash_len;
+    EVP_DigestFinal_ex(mdctx, hash, &hash_len);
+
+	// make hexadecimal string of sha256 hash
+	char hash_hex[SHA256_DIGEST_LENGTH * 2 + 1];
+	for(int i = 0; i < SHA256_DIGEST_LENGTH; i++) {
+        sprintf(hash_hex + i*2,"%02x", hash[i]);
+    }
+	hash_hex[SHA256_DIGEST_LENGTH * 2] = '\0';
+
+	// confirm that checksum matches
+	assert(source->checksum != NULL); 
+	if (strcmp(source->checksum, hash_hex) == 0) {
+		print("checksum verified for download: %s\n", hash_hex);
+		return true;
+	} else {
+		print("FAIL: bad checksum for download: %s\n", hash_hex);
+		goto fail;
+	}
+
+fail:
+    if (access(source_path, F_OK) == 0) remove(source_path);
+	free(source_path);
+	return false;
+}
+
+static size_t download_write_callback(char* ptr, size_t size, size_t nmemb, void* usrdata) {
+	// write the curl data to the file in usr data
+	size_t written = fwrite(ptr, size, nmemb, (FILE *)usrdata);
+
+	// update the hash with the new data
+    EVP_DigestUpdate(mdctx, ptr, written);
+
+	return written;
+}
+
+void ensure_libcrypto() {
+	if (mdctx == NULL) {
+		mdctx = EVP_MD_CTX_new();
+		md = EVP_sha256();
+		/* come back to this if we have init and deinit */
+		/* EVP_MD_CTX_free(mdctx); */
+	}
+}
+
+void ensure_libcurl() {
+	if (curl == NULL) {
+		CURLcode result = curl_global_init(CURL_GLOBAL_ALL);
+		if (result != CURLE_OK) die("failed to initialize curl: %s", curl_easy_strerror(result));
+		curl = curl_easy_init(); // note(jqj): for now we reuse one easy curl object
+		if (curl == NULL) die("failed to initialize easy curl");
+		/* come back to this if we have init and deinit */
+		/* curl_easy_cleanup(curl); */
+		/* curl_global_cleanup(); */
+	}
+}
-- 
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