From 615e3302c9dd358bb64cd56d1f3814ad8d5df84d Mon Sep 17 00:00:00 2001
From: vetch <vetch97@gmail.com>
Date: Sat, 4 Jan 2020 19:37:32 +0100
Subject: rearranged files, updated makefile

---
 src/memory/makefs.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 src/memory/makefs.c

(limited to 'src/memory/makefs.c')

diff --git a/src/memory/makefs.c b/src/memory/makefs.c
new file mode 100644
index 0000000..379e8c5
--- /dev/null
+++ b/src/memory/makefs.c
@@ -0,0 +1,97 @@
+// Take files given on stdin and make them into a ramfs image of our
+// own, (stupid) simple format.
+// In the format: for each file comes the null-terminated string
+// with filename, then null-padding until a 4-aligned offset, then
+// 4-byte little-endian size of the file and then the contents
+// of the file and then another null-padding until a 4-aligned offset.
+// Files encoded this way go one after another (so it's easy to add
+// something at the beginning).
+// At the and comes one null-byte (as if a file with empty name
+// was there).
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <err.h>
+#include <sys/stat.h>
+#include <string.h>
+
+#define ANSI_FG_RED "\033[0;31m"
+#define ANSI_FG_DEFAULT "\033[0;39m"
+
+int main(int argc, char **argv)
+{
+  // process files in the order they are provided on the command line
+  for (int i = 1; i < argc; i++)
+    {
+      struct stat fileinfo;
+      
+      if (stat(argv[i], &fileinfo))
+	err(-1, "couldn't stat " ANSI_FG_RED "%s" ANSI_FG_DEFAULT,
+	    argv[i]);
+	
+      if (!S_ISREG(fileinfo.st_mode))
+	errx(-1, ANSI_FG_RED "%s" ANSI_FG_DEFAULT
+	     " is not a regular file.", argv[i]);
+
+      // don't allow files with size so big, that it can't be encoded
+      // in a 4-byte unsigned int... In practice even smaller files
+      // won't fit on the rpi.
+      if (fileinfo.st_size > UINT32_MAX)
+	errx(-1, ANSI_FG_RED "%s" ANSI_FG_DEFAULT
+	     " is too big.", argv[i]);
+      
+      uint32_t file_size = fileinfo.st_size;
+      uint32_t name_size = strlen(argv[i]) + 1; // 1 for null-byte
+      
+      if (fwrite(argv[i], 1, name_size, stdout) != name_size)
+	errx(-1, "error writing to stdout");
+
+      // pad with null-bytes until a 4-aligned offset
+      for (uint32_t j = 0; (j + name_size) & 0b11; j++)
+	if (putchar('\0'))
+	  errx(-1, "error writing to stdout");	  
+
+      // TODO convert file_size to little endian first (in case our
+      // host is be).
+      if (fwrite(&file_size, 4, 1, stdout) != 1)
+	errx(-1, "error writing to stdout");
+
+      // flush b4 running cat, so that stuff we've written comes
+      // b4 the actual file contents in the output
+      if (fflush(stdout))
+	err(-1, "couldn't flush stdout");
+
+      // we don't copy the actual file ourselves - we run cat for that
+      pid_t pid;
+      int wstatus;
+      switch (pid = fork())
+	{
+	case -1:
+	  err(-1, "couldn't fork");
+	case 0:
+	  if (execlp("cat", "cat", argv[i], NULL))
+	    err(-1, "couldn't execute cat");
+	default:
+	  if (wait(&wstatus) == -1)
+	    err(-1, "error waiting for child");
+
+	  if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus))
+	    exit(-1);
+	}
+
+      // again, pad with null-bytes until a 4-aligned offset
+      for (uint32_t j = 0; (j + file_size) & 0b11; j++)
+	if (putchar('\0'))
+	  errx(-1, "error writing to stdout");
+    }
+  
+  if (putchar('\0'))
+    errx(-1, "error writing to stdout");
+  
+  return 0;
+}
+
-- 
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