libstore: rename confusing const identifiers

Also adds an assert that store path hash part length is what we expect
because it's alarmingly easy to forget to truncate a hash before
throwing it into there. It's kind of messy code, someone could improve
it more later.

Change-Id: I5296ea3d5b854323d092f0256defb598dd5b87e8

lix/libstore/local-store.cc

@@ -911,7 +911,9 @@ try {
 kj::Promise<Result<std::optional<StorePath>>>
 LocalStore::queryPathFromHashPart(const std::string & hashPart)
 try {
-    if (hashPart.size() != StorePath::HashLen) throw Error("invalid hash part");
+    if (hashPart.size() != StorePath::HASH_PART_LEN) {
+        throw Error("invalid hash part");
+    }
 
     Path prefix = config_.storeDir + "/" + hashPart;
 

lix/libstore/path-tree.cc

@@ -76,7 +76,7 @@ try {
                                 std::string(contents, pos2, pos - pos2 + hash.size() + margin)
                             ),
                             pos - pos2,
-                            StorePath::HashLen,
+                            StorePath::HASH_PART_LEN,
                             getColour(hash)
                         ))
                 );
@@ -88,9 +88,9 @@ try {
         for (auto & hash : hashes) {
             auto pos = target.find(hash);
             if (pos != std::string::npos) {
-                hits[hash].emplace_back(
-                    fmt("%s -> %s", p2, hilite(target, pos, StorePath::HashLen, getColour(hash)))
-                );
+                hits[hash].emplace_back(fmt(
+                    "%s -> %s", p2, hilite(target, pos, StorePath::HASH_PART_LEN, getColour(hash))
+                ));
             }
         }
     }

lix/libstore/path.cc

@@ -8,9 +8,11 @@ static void checkName(std::string_view path, std::string_view name)
 {
     if (name.empty())
         throw BadStorePath("store path '%s' has an empty name", path);
-    if (name.size() > StorePath::MaxPathLen)
-        throw BadStorePath("store path '%s' has a name longer than %d characters",
-            path, StorePath::MaxPathLen);
+    if (name.size() > StorePath::MAX_PATH_LEN) {
+        throw BadStorePath(
+            "store path '%s' has a name longer than %d characters", path, StorePath::MAX_PATH_LEN
+        );
+    }
     // See nameRegexStr for the definition
     if (name[0] == '.') {
         // check against "." and "..", followed by end or dash
@@ -36,8 +38,9 @@ static void checkName(std::string_view path, std::string_view name)
 StorePath::StorePath(std::string_view _baseName)
     : baseName(_baseName)
 {
-    if (baseName.size() < HashLen + 1)
+    if (baseName.size() < HASH_PART_LEN + 1) {
         throw BadStorePath("'%s' is too short to be a valid store path", baseName);
+    }
     for (auto c : hashPart())
         if (c == 'e' || c == 'o' || c == 'u' || c == 't'
             || !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'z')))
@@ -48,6 +51,7 @@ StorePath::StorePath(std::string_view _baseName)
 StorePath::StorePath(const Hash & hash, std::string_view _name)
     : baseName((hash.to_string(Base::Base32, false) + "-").append(std::string(_name)))
 {
+    assert(hash.base32Len() == HASH_PART_LEN);
     checkName(baseName, name());
 }
 

lix/libstore/path.hh

@@ -26,9 +26,9 @@ public:
     /**
      * Size of the hash part of store paths, in base-32 characters.
      */
-    constexpr static size_t HashLen = 32; // i.e. 160 bits
+    constexpr static size_t HASH_PART_LEN = 32; // i.e. 160 bits
 
-    constexpr static size_t MaxPathLen = 211;
+    constexpr static size_t MAX_PATH_LEN = 211;
 
     StorePath() = delete;
 
@@ -63,12 +63,12 @@ public:
 
     std::string_view name() const
     {
-        return std::string_view(baseName).substr(HashLen + 1);
+        return std::string_view(baseName).substr(HASH_PART_LEN + 1);
     }
 
     std::string_view hashPart() const
     {
-        return std::string_view(baseName).substr(0, HashLen);
+        return std::string_view(baseName).substr(0, HASH_PART_LEN);
     }
 
     static StorePath dummy;