From d9c893af11601efaee82cb8f18b2dc3d0097b238 Mon Sep 17 00:00:00 2001
From: Geza Lore <gezalore@gmail.com>
Date: Tue, 20 Jul 2021 14:18:35 +0100
Subject: [PATCH] Internals: Add VString::startsWith predicate function

---
 src/V3OptionParser.cpp |  8 +++-----
 src/V3PreProc.cpp      | 14 +++++++-------
 src/V3String.cpp       |  4 ++++
 src/V3String.h         |  2 ++
 4 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/src/V3OptionParser.cpp b/src/V3OptionParser.cpp
index c6eec718c..f1db000af 100644
--- a/src/V3OptionParser.cpp
+++ b/src/V3OptionParser.cpp
@@ -120,14 +120,12 @@ V3OptionParser::ActionIfs* V3OptionParser::find(const char* optp) {
     if (it != m_pimpl->m_options.end()) return it->second.get();
     for (auto&& act : m_pimpl->m_options) {
         if (act.second->isOnOffAllowed()) {  // Find starts with "-no"
-            const char* const nop = std::strncmp(optp, "-no", 3) ? nullptr : (optp + 3);
+            const char* const nop = VString::startsWith(optp, "-no") ? (optp + 3) : nullptr;
             if (nop && (act.first == nop || act.first == (string{"-"} + nop))) {
                 return act.second.get();
             }
         } else if (act.second->isPartialMatchAllowed()) {
-            if (!std::strncmp(optp, act.first.c_str(), act.first.length())) {
-                return act.second.get();
-            }
+            if (VString::startsWith(optp, act.first)) return act.second.get();
         }
     }
     return nullptr;
@@ -148,7 +146,7 @@ V3OptionParser::ActionIfs& V3OptionParser::add(const std::string& opt, ARG arg)
 bool V3OptionParser::hasPrefixNo(const char* strp) {
     UASSERT(strp[0] == '-', strp << " does not start with '-'");
     if (strp[1] == '-') ++strp;
-    return std::strncmp(strp, "-no", 3) == 0;
+    return VString::startsWith(strp, "-no");
 }
 
 int V3OptionParser::parse(int idx, int argc, char* argv[]) {
diff --git a/src/V3PreProc.cpp b/src/V3PreProc.cpp
index 3bf62d303..02dbeeaa4 100644
--- a/src/V3PreProc.cpp
+++ b/src/V3PreProc.cpp
@@ -395,7 +395,7 @@ string V3PreProcImp::commentCleanup(const string& text) {
 
 bool V3PreProcImp::commentTokenMatch(string& cmdr, const char* strg) {
     int len = strlen(strg);
-    if (0 == strncmp(cmdr.c_str(), strg, len) && (cmdr[len] == '\0' || isspace(cmdr[len]))) {
+    if (VString::startsWith(cmdr, strg) && (cmdr[len] == '\0' || isspace(cmdr[len]))) {
         if (isspace(cmdr[len])) len++;
         cmdr = cmdr.substr(len);
         return true;
@@ -423,27 +423,27 @@ void V3PreProcImp::comment(const string& text) {
 
     bool synth = false;
     bool vlcomment = false;
-    if ((cp[0] == 'v' || cp[0] == 'V') && 0 == (strncmp(cp + 1, "erilator", 8))) {
+    if ((cp[0] == 'v' || cp[0] == 'V') && VString::startsWith(cp + 1, "erilator")) {
         cp += strlen("verilator");
         if (*cp == '_') {
             fileline()->v3error("Extra underscore in meta-comment;"
                                 " use /*verilator {...}*/ not /*verilator_{...}*/");
         }
         vlcomment = true;
-    } else if (0 == (strncmp(cp, "synopsys", strlen("synopsys")))) {
+    } else if (VString::startsWith(cp, "synopsys")) {
         cp += strlen("synopsys");
         synth = true;
         if (*cp == '_') {
             fileline()->v3error("Extra underscore in meta-comment;"
                                 " use /*synopsys {...}*/ not /*synopsys_{...}*/");
         }
-    } else if (0 == (strncmp(cp, "cadence", strlen("cadence")))) {
+    } else if (VString::startsWith(cp, "cadence")) {
         cp += strlen("cadence");
         synth = true;
-    } else if (0 == (strncmp(cp, "pragma", strlen("pragma")))) {
+    } else if (VString::startsWith(cp, "pragma")) {
         cp += strlen("pragma");
         synth = true;
-    } else if (0 == (strncmp(cp, "ambit synthesis", strlen("ambit synthesis")))) {
+    } else if (VString::startsWith(cp, "ambit synthesis")) {
         cp += strlen("ambit synthesis");
         synth = true;
     } else {
@@ -1544,7 +1544,7 @@ int V3PreProcImp::getFinalToken(string& buf) {
     // Track `line
     const char* bufp = buf.c_str();
     while (*bufp == '\n') bufp++;
-    if ((tok == VP_TEXT || tok == VP_LINE) && 0 == strncmp(bufp, "`line ", 6)) {
+    if ((tok == VP_TEXT || tok == VP_LINE) && VString::startsWith(bufp, "`line ")) {
         int enter;
         m_finFilelinep->lineDirective(bufp, enter /*ref*/);
     } else {
diff --git a/src/V3String.cpp b/src/V3String.cpp
index c4f054575..caf5a8283 100644
--- a/src/V3String.cpp
+++ b/src/V3String.cpp
@@ -174,6 +174,10 @@ string VString::replaceWord(const string& str, const string& from, const string&
     return result;
 }
 
+bool VString::startsWith(const string& str, const string& prefix) {
+    return str.rfind(prefix, 0) == 0;  // Faster than .find(_) == 0
+}
+
 //######################################################################
 // VHashSha256
 
diff --git a/src/V3String.h b/src/V3String.h
index f3ed2f651..e028561f3 100644
--- a/src/V3String.h
+++ b/src/V3String.h
@@ -113,6 +113,8 @@ public:
     // to be a consecutive sequence of the characters [a-zA-Z0-9_]. Sub-words are not replaced.
     // e.g.: replaceWords("one apple bad_apple", "apple", "banana") -> "one banana bad_apple"
     static string replaceWord(const string& str, const string& from, const string& to);
+    // Predicate to check if 'str' starts with 'prefix'
+    static bool startsWith(const string& str, const string& prefix);
 };
 
 //######################################################################