Packages (nix): use hash to cache count and process count manually (#817)

Author: xoltia

src/detection/packages/packages_linux.c

@@ -118,28 +118,152 @@ static uint32_t countFilesRecursive(FFstrbuf* baseDir, const char* dirname, cons
     return sum;
 }
 
+static bool isValidNixPkg(FFstrbuf* pkg)
+{
+    if (!ffPathExists(pkg->chars, FF_PATHTYPE_DIRECTORY))
+        return false;
+
+    ffStrbufSubstrAfterLastC(pkg, '/');
+    if (
+        ffStrbufStartsWithS(pkg, "nixos-system-nixos-") ||
+        ffStrbufEndsWithS(pkg, "-doc") ||
+        ffStrbufEndsWithS(pkg, "-man") ||
+        ffStrbufEndsWithS(pkg, "-info") ||
+        ffStrbufEndsWithS(pkg, "-dev") ||
+        ffStrbufEndsWithS(pkg, "-bin")
+    ) return false;
+
+    enum { START, DIGIT, DOT, MATCH } state = START;
+
+    for (uint32_t i = 0; i < pkg->length; i++)
+    {
+        char c = pkg->chars[i];
+        switch (state)
+        {
+            case START:
+                if (c >= '0' && c <= '9')
+                    state = DIGIT;
+                break;
+            case DIGIT:
+                if (c >= '0' && c <= '9')
+                    continue;
+                if (c == '.')
+                    state = DOT;
+                else
+                    state = START;
+                break;
+            case DOT:
+                if (c >= '0' && c <= '9')
+                    state = MATCH;
+                else
+                    state = START;
+                break;
+            case MATCH:
+                break;
+        }
+    }
+
+    return state == MATCH;
+}
+
+static bool checkNixCache(FFstrbuf* cacheDir, FFstrbuf* hash, uint32_t* count)
+{
+    if (!ffPathExists(cacheDir->chars, FF_PATHTYPE_FILE))
+        return false;
+
+    FF_STRBUF_AUTO_DESTROY cacheContent;
+    ffStrbufInit(&cacheContent);
+    if (!ffReadFileBuffer(cacheDir->chars, &cacheContent))
+        return false;
+
+    // Format: <hash>\n<count>
+    uint32_t split = ffStrbufFirstIndexC(&cacheContent, '\n');
+    if (split == cacheContent.length)
+        return false;
+
+    ffStrbufSetNS(hash, split, cacheContent.chars);
+    *count = (uint32_t)atoi(cacheContent.chars + split + 1);
+
+    return true;
+}
+
+static bool writeNixCache(FFstrbuf* cacheDir, FFstrbuf* hash, uint32_t count)
+{
+    FF_STRBUF_AUTO_DESTROY cacheContent;
+    ffStrbufInit(&cacheContent);
+    ffStrbufAppend(&cacheContent, hash);
+    ffStrbufAppendC(&cacheContent, '\n');
+    ffStrbufAppendF(&cacheContent, "%u", count);
+    return ffWriteFileBuffer(cacheDir->chars, &cacheContent);
+}
+
 static uint32_t getNixPackagesImpl(char* path)
 {
     //Nix detection is kinda slow, so we only do it if the dir exists
     if(!ffPathExists(path, FF_PATHTYPE_DIRECTORY))
         return 0;
 
-    FF_STRBUF_AUTO_DESTROY output = ffStrbufCreateA(128);
+    FF_STRBUF_AUTO_DESTROY cacheDir;
+    ffStrbufInit(&cacheDir);
+    ffStrbufAppend(&cacheDir, &instance.state.platform.cacheDir);
+    ffStrbufEnsureEndsWithC(&cacheDir, '/');
+    ffStrbufAppendS(&cacheDir, "fastfetch/packages/nix");
+    ffStrbufAppendS(&cacheDir, path);
+
+    //Check the hash first to determine if we need to recompute the count
+    FF_STRBUF_AUTO_DESTROY hash = ffStrbufCreateA(64);
+    FF_STRBUF_AUTO_DESTROY cacheHash = ffStrbufCreateA(64);
+    uint32_t count = 0;
+
+    ffProcessAppendStdOut(&hash, (char* const[]) {
+        "nix-store",
+        "--query",
+        "--hash",
+        path,
+        NULL
+    });
+
+    if (checkNixCache(&cacheDir, &cacheHash, &count) && ffStrbufEqual(&hash, &cacheHash))
+        return count;
 
+    //Cache is invalid, recompute the count
+    count = 0;
+
+    //Implementation based on bash script from here:
     //https://github.com/fastfetch-cli/fastfetch/issues/195#issuecomment-1191748222
-    FF_STRBUF_AUTO_DESTROY command = ffStrbufCreateA(255);
-    ffStrbufAppendS(&command, "for x in $(nix-store --query --requisites ");
-    ffStrbufAppendS(&command, path);
-    ffStrbufAppendS(&command, "); do if [ -d $x ]; then echo $x ; fi ; done | cut -d- -f2- | egrep '([0-9]{1,}\\.)+[0-9]{1,}' | egrep -v '\\-doc$|\\-man$|\\-info$|\\-dev$|\\-bin$|^nixos-system-nixos-' | uniq | wc -l");
+    
+    FF_STRBUF_AUTO_DESTROY output = ffStrbufCreateA(1024);
 
     ffProcessAppendStdOut(&output, (char* const[]) {
-        "sh",
-        "-c",
-        command.chars,
+        "nix-store",
+        "--query",
+        "--requisites",
+        path,
         NULL
     });
 
-    return (uint32_t) strtol(output.chars, NULL, 10);
+    uint32_t lineLength = 0;
+    for (uint32_t i = 0; i < output.length; i++)
+    {
+        if (output.chars[i] != '\n')
+        {
+            lineLength++;
+            continue;
+        }
+
+        output.chars[i] = '\0';
+        FFstrbuf line = {
+            .allocated = 0,
+            .length = lineLength,
+            .chars = output.chars + i - lineLength
+        };
+        if (isValidNixPkg(&line))
+            count++;
+        lineLength = 0;
+    }
+    
+    writeNixCache(&cacheDir, &hash, count);
+    return count;
 }
 
 static uint32_t getNixPackages(FFstrbuf* baseDir, const char* dirname)