better handling of office documents per #1

R/check-office.R

@@ -0,0 +1,32 @@
+check_office <- function(hdr, path) {
+
+  # [Content_Types.xml] || length 19
+  c(
+    0x5b,0x43,0x6f,0x6e,0x74,0x65,0x6e,0x74,0x5f,0x54,
+    0x79,0x70,0x65,0x73,0x5d,0x2e,0x78,0x6d,0x6c
+  ) -> pat_content_types
+
+  # _rels/.rels || length 11
+  pat_rels <- c(0x5f,0x72,0x65,0x6c,0x73,0x2f,0x2e,0x72,0x65,0x6c,0x73)
+
+  if ((all(pat_content_types == hdr[31:49])) || (all(pat_rels == hdr[31:41]))) {
+
+    hdr <- readBin(path, "raw", n=4096)
+
+    pat_word <- c(0x77,0x6f,0x72,0x64,0x2f)
+    if (length(seq_in(hdr, pat_word)) > 0)
+      return("application/vnd.openxmlformats-officedocument.wordprocessingml.document")
+
+    pat_ppt <- c(0x70,0x70,0x74,0x2f)
+    if (length(seq_in(hdr, pat_ppt)) > 0)
+      return("application/vnd.openxmlformats-officedocument.presentationml.presentation")
+
+    pat_xl <- c(0x78,0x6c,0x2f)
+    if (length(seq_in(hdr, pat_xl)) > 0)
+      return("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
+
+  }
+
+  return(NULL)
+
+}

R/get-content-type.R

@@ -92,9 +92,15 @@ get_content_type <- function(path) {
   if (all(c(0x52,0x49,0x46,0x46) == hdr[1:4])) return("audio/x-wav") # "RIFF"
 
   if (all(c(0x50, 0x4b) == hdr[1:2])) { # "PK"
+
+    office_type <- check_office(hdr, path)
+    if (length(office_type) > 0) return(office_type)
+
     guessed_name <- guess_content_type(path)
     if ((length(guessed_name) == 1) && (guessed_name != "???")) return(guessed_name)
+
     return("application/zip")
+
   }
 
   if (all(c(0x5a,0x4d) == hdr[1:2])) return("x-system/exe")

R/util.R

@@ -0,0 +1,13 @@
+seq_in <- function(a, b) {
+
+  which(
+    Reduce(
+      '+',
+      lapply(
+        seq_along(y <- lapply(b, '==', a)),
+        function(x) { y[[x]][x:(length(a) - length(b) +x)] }
+      )
+    ) == length(b)
+  )
+
+}