Add tests for examples from Nim in Action.

tests/niminaction/Chapter6/WikipediaStats/concurrency_regex.nim

@@ -0,0 +1,64 @@
+# See this page for info about the format https://wikitech.wikimedia.org/wiki/Analytics/Data/Pagecounts-all-sites
+import tables, parseutils, strutils, threadpool, re
+
+const filename = "pagecounts-20160101-050000"
+
+type
+  Stats = ref object
+    projectName, pageTitle: string
+    requests, contentSize: int
+
+proc `$`(stats: Stats): string =
+  "(projectName: $#, pageTitle: $#, requests: $#, contentSize: $#)" % [
+    stats.projectName, stats.pageTitle, $stats.requests, $stats.contentSize
+  ]
+
+proc parse(chunk: string): Stats =
+  # Each line looks like: en Main_Page 242332 4737756101
+  result = Stats(projectName: "", pageTitle: "", requests: 0, contentSize: 0)
+
+  var matches: array[4, string]
+  var reg = re"([^\s]+)\s([^\s]+)\s(\d+)\s(\d+)"
+  for line in chunk.splitLines:
+
+    let start = find(line, reg, matches)
+    if start == -1: continue
+
+    let requestsInt = matches[2].parseInt
+    if requestsInt > result.requests and matches[0] == "en":
+      result = Stats(
+        projectName: matches[0],
+        pageTitle: matches[1],
+        requests: requestsInt,
+        contentSize: matches[3].parseInt
+      )
+
+proc readChunks(filename: string, chunksize = 1000000): Stats =
+  result = Stats(projectName: "", pageTitle: "", requests: 0, contentSize: 0)
+  var file = open(filename)
+  var responses = newSeq[FlowVar[Stats]]()
+  var buffer = newString(chunksize)
+  var oldBufferLen = 0
+  while not endOfFile(file):
+    let readSize = file.readChars(buffer, oldBufferLen, chunksize - oldBufferLen) + oldBufferLen
+    var chunkLen = readSize
+
+    while chunkLen >= 0 and buffer[chunkLen - 1] notin NewLines:
+      # Find where the last line ends
+      chunkLen.dec
+
+    responses.add(spawn parse(buffer[0 .. <chunkLen]))
+    oldBufferLen = readSize - chunkLen
+    buffer[0 .. <oldBufferLen] = buffer[readSize - oldBufferLen .. ^1]
+
+  echo("Spawns: ", responses.len)
+  for resp in responses:
+    let statistic = ^resp
+    if statistic.requests > result.requests:
+      result = statistic
+
+  file.close()
+
+
+when isMainModule:
+  echo readChunks(filename)