(Re)add support for tar-writing to microtar

soedinglab · Sep 20, 2022 · dcd180b · dcd180b
1 parent fea8d20
commit dcd180b
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Showing 3 changed files with 102 additions and 4 deletions.
diff --git a/lib/microtar/microtar.c b/lib/microtar/microtar.c
@@ -64,6 +64,7 @@ const char* mtar_strerror(int err) {
     case MTAR_EFAILURE     : return "failure";
     case MTAR_EOPENFAIL    : return "could not open";
     case MTAR_EREADFAIL    : return "could not read";
+    case MTAR_EWRITEFAIL   : return "could not write";
     case MTAR_ESEEKFAIL    : return "could not seek";
     case MTAR_EBADCHKSUM   : return "bad checksum";
     case MTAR_ENULLRECORD  : return "null record";
@@ -72,6 +73,11 @@ const char* mtar_strerror(int err) {
   return "unknown error";
 }
 
+static int file_write(mtar_t *tar, const void *data, size_t size) {
+  size_t res = fwrite(data, 1, size, (FILE*)tar->stream);
+  return (res == size) ? MTAR_ESUCCESS : MTAR_EWRITEFAIL;
+}
+
 static int file_read(mtar_t *tar, void *data, size_t size) {
   size_t res = fread(data, 1, size, (FILE*)tar->stream);
   return (res == size) ? MTAR_ESUCCESS : MTAR_EREADFAIL;
@@ -87,15 +93,19 @@ static int file_close(mtar_t *tar) {
   return MTAR_ESUCCESS;
 }
 
-int mtar_open(mtar_t *tar, const char *filename) {
+int mtar_open(mtar_t *tar, const char *filename, const char* mode) {
   /* Init tar struct and functions */
   memset(tar, 0, sizeof(*tar));
   tar->read = file_read;
+  tar->write = file_write;
   tar->seek = file_seek;
   tar->close = file_close;
 
   /* Open file */
-  tar->stream = fopen(filename, "rb");
+  if ( strchr(mode, 'r') ) mode = "rb";
+  if ( strchr(mode, 'w') ) mode = "wb";
+  if ( strchr(mode, 'a') ) mode = "ab";
+  tar->stream = fopen(filename, mode);
   if (!tar->stream) {
     return MTAR_EOPENFAIL;
   }
@@ -173,3 +183,81 @@ int mtar_read_data(mtar_t *tar, void *ptr, size_t size) {
   }
   return MTAR_ESUCCESS;
 }
+
+int mtar_write_header(mtar_t *tar, const mtar_header_t *h) {
+  /* Build raw header and write */
+  mtar_raw_header_t rh;
+  memset(&rh, 0, sizeof(rh));
+  sprintf(rh.mode, "%o", h->mode);
+  sprintf(rh.owner, "%o", h->owner);
+  sprintf(rh.size, "%o", h->size);
+  sprintf(rh.mtime, "%o", h->mtime);
+  rh.type = h->type ? h->type : MTAR_TREG;
+  strcpy(rh.name, h->name);
+  strcpy(rh.linkname, h->linkname);
+
+  /* Calculate and write checksum */
+  unsigned chksum = checksum(&rh);
+  sprintf(rh.checksum, "%06o", chksum);
+  rh.checksum[7] = ' ';
+
+  tar->remaining_data = h->size;
+  int err = tar->write(tar, &rh, sizeof(rh));
+  tar->pos += sizeof(rh);
+  return err;
+}
+
+int mtar_write_file_header(mtar_t *tar, const char *name, size_t size) {
+  mtar_header_t h;
+  /* Build header */
+  memset(&h, 0, sizeof(h));
+  strcpy(h.name, name);
+  h.size = size;
+  h.type = MTAR_TREG;
+  h.mode = 0644;
+  /* Write header */
+  return mtar_write_header(tar, &h);
+}
+
+int mtar_write_dir_header(mtar_t *tar, const char *name) {
+  mtar_header_t h;
+  /* Build header */
+  memset(&h, 0, sizeof(h));
+  strcpy(h.name, name);
+  h.type = MTAR_TDIR;
+  h.mode = 0755;
+  /* Write header */
+  return mtar_write_header(tar, &h);
+}
+
+static int write_null_bytes(mtar_t *tar, int n) {
+  char nul = '\0';
+  for (int i = 0; i < n; i++) {
+    int err = tar->write(tar, &nul, 1);
+    tar->pos++;
+    if (err) {
+      return err;
+    }
+  }
+  return MTAR_ESUCCESS;
+}
+
+int mtar_write_data(mtar_t *tar, const void *data, size_t size) {
+  /* Write data */
+  int err = tar->write(tar, data, size);
+  tar->pos += size;
+  if (err) {
+    return err;
+  }
+  tar->remaining_data -= size;
+  /* Write padding if we've written all the data for this file */
+  if (tar->remaining_data == 0) {
+    return write_null_bytes(tar, round_up(tar->pos, 512) - tar->pos);
+  }
+  return MTAR_ESUCCESS;
+}
+
+int mtar_write_finalize(mtar_t *tar) {
+  /* Write two NULL records */
+  return write_null_bytes(tar, sizeof(mtar_raw_header_t) * 2);
+}
diff --git a/lib/microtar/microtar.h b/lib/microtar/microtar.h
@@ -23,6 +23,7 @@ enum {
   MTAR_EFAILURE     = -1,
   MTAR_EOPENFAIL    = -2,
   MTAR_EREADFAIL    = -3,
+  MTAR_EWRITEFAIL   = -4,
   MTAR_ESEEKFAIL    = -5,
   MTAR_EBADCHKSUM   = -6,
   MTAR_ENULLRECORD  = -7,
@@ -58,23 +59,32 @@ typedef struct mtar_t mtar_t;
 
 struct mtar_t {
   int (*read)(mtar_t *tar, void *data, size_t size);
+  int (*write)(mtar_t *tar, const void *data, size_t size);
   int (*seek)(mtar_t *tar, long pos, int whence);
   int (*close)(mtar_t *tar);
   void *stream;
   size_t curr_size;
+  size_t pos;
+  size_t remaining_data;
   int isFinished;
 };
 
 
 const char* mtar_strerror(int err);
 
-int mtar_open(mtar_t *tar, const char *filename);
+int mtar_open(mtar_t *tar, const char *filename, const char* mode);
 int mtar_close(mtar_t *tar);
 
 int mtar_read_header(mtar_t *tar, mtar_header_t *h);
 int mtar_read_data(mtar_t *tar, void *ptr, size_t size);
 int mtar_skip_data(mtar_t *tar);
 
+int mtar_write_header(mtar_t *tar, const mtar_header_t *h);
+int mtar_write_file_header(mtar_t *tar, const char *name, size_t size);
+int mtar_write_dir_header(mtar_t *tar, const char *name);
+int mtar_write_data(mtar_t *tar, const void *data, size_t size);
+int mtar_write_finalize(mtar_t *tar);
+
 #ifdef __cplusplus
 }
 #endif

diff --git a/src/util/tar2db.cpp b/src/util/tar2db.cpp
@@ -113,7 +113,7 @@ int tar2db(int argc, const char **argv, const Command& command) {
             EXIT(EXIT_FAILURE);
 #endif
         } else {
-            if (mtar_open(&tar, filenames[i].c_str()) != MTAR_ESUCCESS) {
+            if (mtar_open(&tar, filenames[i].c_str(), "r") != MTAR_ESUCCESS) {
                 Debug(Debug::ERROR) << "Cannot open file " << filenames[i] << "\n";
                 EXIT(EXIT_FAILURE);
             }