From 90ff57010b59be548e67b6d49353d2ec3b6c4cff Mon Sep 17 00:00:00 2001
From: Francois Fleuret <francois@fleuret.org>
Date: Mon, 6 Apr 2009 08:05:43 +0200
Subject: [PATCH] Added some comments in the hash-table routines.

---
 selector.cc | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/selector.cc b/selector.cc
index 71768e7..9c863a4 100644
--- a/selector.cc
+++ b/selector.cc
@@ -87,6 +87,10 @@ void check_opt(int argc, char **argv, int n_opt, int n, const char *help) {
 //////////////////////////////////////////////////////////////////////
 // A quick and dirty hash table
 
+// The table itself stores index of the strings in a char
+// **table. When a string is added, if it was already in the table,
+// the new index replaces the previous one.
+
 int *new_hash_table(int hash_table_size) {
   int *result;
   result = new int[hash_table_size];
@@ -96,6 +100,10 @@ int *new_hash_table(int hash_table_size) {
   return result;
 }
 
+// Adds new_string in the table, associated to new_index. If this
+// string was not already in the table, returns -1. Otherwise, returns
+// the previous index it had.
+
 int test_and_add(char *new_string, int new_index,
                  char **strings, int *hash_table, int hash_table_size) {
   unsigned int code = 0;
@@ -110,16 +118,23 @@ int test_and_add(char *new_string, int new_index,
   code = code % hash_table_size;
 
   while(hash_table[code] >= 0) {
+    // There is a string with that code
     if(strcmp(new_string, strings[hash_table[code]]) == 0) {
+      // It is the same string, we keep a copy of the stored index
       int result = hash_table[code];
+      // Put the new one
       hash_table[code] = new_index;
+      // And return the previous one
       return result;
     }
+    // This collision was not the same string, let's move to the next
+    // in the table
     code = (code + 1) % hash_table_size;
   }
 
+  // This string was not already in there, store the index in the
+  // table and return -1
   hash_table[code] = new_index;
-
   return -1;
 }
 
@@ -622,8 +637,8 @@ int main(int argc, char **argv) {
         lines[nb_lines] = new char[strlen(s) + 1];
         strcpy(lines[nb_lines], s);
       } else {
-        // We do not allocate a new string but use the pointer to the
-        // first occurence of it
+        // The string was already in there, so we do not allocate a
+        // new string but use the pointer to the first occurence of it
         lines[nb_lines] = lines[dup];
         lines[dup] = 0;
       }
-- 
2.20.1