- add even more comments

diff --git a/ext/repo_write.c b/ext/repo_write.c
index 13c2502..6ffe996 100644 (file)
--- a/ext/repo_write.c
+++ b/ext/repo_write.c
@@ -1159,7 +1159,7 @@ repo_write(Repo *repo, FILE *fp, int (*keyfilter)(Repo *repo, Repokey *key, void
          if (data->localpool)
            {
              if (poolusage)
-               poolusage = 3;  /* need local pool */
+               poolusage = 3;  /* need own pool */
              else
                {
                  poolusage = 2;
@@ -1171,13 +1171,13 @@ repo_write(Repo *repo, FILE *fp, int (*keyfilter)(Repo *repo, Repokey *key, void
              if (poolusage == 0)
                poolusage = 1;
              else if (poolusage != 1)
-               poolusage = 3;  /* need local pool */
+               poolusage = 3;  /* need own pool */
            }
        }
       if (dirused)
        {
          if (dirpoolusage)
-           dirpoolusage = 3;   /* need local dirpool */
+           dirpoolusage = 3;   /* need own dirpool */
          else
            {
              dirpoolusage = 2;
@@ -1432,26 +1432,35 @@ for (i = 1; i < target.nkeys; i++)
 
 /********************************************************************/
 
-  /* increment need id for used dir components */
-  if (cbdata.dirused && !cbdata.dirused[0])
+  if (dirpool && cbdata.dirused && !cbdata.dirused[0])
     {
       /* no dirs used at all */
       cbdata.dirused = sat_free(cbdata.dirused);
       dirpool = 0;
     }
+
+  /* increment need id for used dir components */
   if (dirpool)
     {
+      /* if we have own dirpool, all entries in it are used.
+        also, all comp ids are already mapped by putinowndirpool(),
+        so we can simply increment needid.
+        (owndirpool != 0, dirused == 0, dirpooldata == 0) */
+      /* else we re-use a dirpool of repodata "dirpooldata".
+        dirused tells us which of the ids are used.
+        we need to map comp ids if we generate a new pool.
+        (owndirpool == 0, dirused != 0, dirpooldata != 0) */
       for (i = 1; i < dirpool->ndirs; i++)
        {
 #if 0
 fprintf(stderr, "dir %d used %d\n", i, cbdata.dirused ? cbdata.dirused[i] : 1);
 #endif
+         if (cbdata.dirused && !cbdata.dirused[i])
+           continue;
          id = dirpool->dirs[i];
          if (id <= 0)
            continue;
-         if (cbdata.dirused && !cbdata.dirused[i])
-           continue;
-         if (cbdata.ownspool && dirpooldata && id > 1)
+         if (dirpooldata && cbdata.ownspool && id > 1)
            {
              id = putinownpool(&cbdata, dirpooldata->localpool ? &dirpooldata->spool : &pool->ss, id);
              needid = cbdata.needid;
@@ -1460,8 +1469,6 @@ fprintf(stderr, "dir %d used %d\n", i, cbdata.dirused ? cbdata.dirused[i] : 1);
        }
     }
 
-  reloff = needid[0].map;
-
 
 /********************************************************************/
 
@@ -1473,7 +1480,7 @@ fprintf(stderr, "dir %d used %d\n", i, cbdata.dirused ? cbdata.dirused[i] : 1);
    */
 
   /* zero out id 0 and rel 0 just in case */
-
+  reloff = needid[0].map;
   needid[0].need = 0;
   needid[reloff].need = 0;
 
@@ -1488,32 +1495,39 @@ fprintf(stderr, "dir %d used %d\n", i, cbdata.dirused ? cbdata.dirused[i] : 1);
   sat_sort(needid + 2, spool->nstrings - 2, sizeof(*needid), needid_cmp_need_s, spool);
 #endif
   sat_sort(needid + reloff, pool->nrels, sizeof(*needid), needid_cmp_need, 0);
+  /* now needid is in new order, needid[newid].map -> oldid */
 
+  /* calculate string space size, also zero out needid[].need */
   sizeid = 0;
   for (i = 1; i < reloff; i++)
     {
       if (!needid[i].need)
-        break;
+        break; /* as we have sorted, every entry after this also has need == 0 */
       needid[i].need = 0;
       sizeid += strlen(spool->stringspace + spool->strings[needid[i].map]) + 1;
     }
+  nstrings = i;        /* our new string id end */
 
-  nstrings = i;
+  /* make needid[oldid].need point to newid */
   for (i = 1; i < nstrings; i++)
     needid[needid[i].map].need = i;
 
+  /* same as above for relations */
   for (i = 0; i < pool->nrels; i++)
     {
       if (!needid[reloff + i].need)
         break;
-      else
-        needid[reloff + i].need = 0;
+      needid[reloff + i].need = 0;
     }
+  nrels = i;   /* our new rel id end */
 
-  nrels = i;
   for (i = 0; i < nrels; i++)
     needid[needid[reloff + i].map].need = nstrings + i;
 
+  /* now we have: needid[oldid].need -> newid
+                  needid[newid].map  -> oldid
+     both for strings and relations  */
+
 
 /********************************************************************/
 
@@ -1526,6 +1540,7 @@ fprintf(stderr, "dir %d used %d\n", i, cbdata.dirused ? cbdata.dirused[i] : 1);
        * directory into single blocks.
        * Instead of components, traverse_dirs stores the old dirids,
        * we will change this in the second step below */
+      /* (dirpooldata and dirused are 0 if we have our own dirpool) */
       if (cbdata.dirused && !cbdata.dirused[1])
        cbdata.dirused[1] = 1;  /* always want / entry */
       dirmap = sat_calloc(dirpool->ndirs, sizeof(Id));
@@ -1543,15 +1558,20 @@ fprintf(stderr, "dir %d used %d\n", i, cbdata.dirused ? cbdata.dirused[i] : 1);
            continue;
          cbdata.dirused[dirmap[i]] = i;
          id = dirpool->dirs[dirmap[i]];
-         if (cbdata.ownspool && dirpooldata && id > 1)
+         if (dirpooldata && cbdata.ownspool && id > 1)
            id = putinownpool(&cbdata, dirpooldata->localpool ? &dirpooldata->spool : &pool->ss, id);
          dirmap[i] = needid[id].need;
        }
-      /* now the new target directory structure is complete, and we have
-       * dirused[] to map from old dirids to new dirids */
+      /* now the new target directory structure is complete (dirmap), and we have
+       * dirused[olddirid] -> newdirid */
     }
 
 /********************************************************************/
+
+  /* collect all data
+   * we use extdata[0] for incore data and extdata[keyid] for vertical data
+   */
+
   cbdata.extdata = sat_calloc(target.nkeys, sizeof(struct extdata));
 
   xd = cbdata.extdata;
@@ -1797,12 +1817,13 @@ fprintf(stderr, "dir %d used %d\n", i, cbdata.dirused ? cbdata.dirused[i] : 1);
     write_blob(fp, cbdata.extdata[0].buf, cbdata.extdata[0].len);
   sat_free(cbdata.extdata[0].buf);
 
-  /* write vertical data */
+  /* do we have vertical data? */
   for (i = 1; i < target.nkeys; i++)
     if (cbdata.extdata[i].len)
       break;
   if (i < target.nkeys)
     {
+      /* yes, write it in pages */
       unsigned char *dp, vpage[BLOB_PAGESIZE];
       int l, ll, lpage = 0;