Add: initrd filesystem utilities (ls, cat) + docs

src/kernel/initrd.c

@@ -0,0 +1,104 @@
+// Initial TAR ramdisk kernel module 
+// Author: xamidev
+// Licensed under the Unlicense. See the repo below.
+// https://github.com/xamidev/blankos
+
+#include "../libc/stdio.h"
+#include <stdint.h>
+#include "../libc/string.h"
+#include "initrd.h"
+#include "system.h"
+
+static unsigned int octal_to_int(const char* str, size_t size)
+{
+	unsigned int result = 0;
+	while (*str && size-- > 0)
+	{
+		result = (result << 3) | (*str - '0');
+		str++;
+	}
+	return result;
+}
+
+uint32_t tar_parse_size(const char* in)
+{
+	uint32_t size = 0;
+	while (*in >= '0' && *in <= '7')
+	{
+		size = (size*8) + (*in - '0');
+		in++;
+	}
+	return size;
+}
+
+void tar_find_file(uint8_t *tar_start, const char* filename)
+{
+	uint8_t *ptr = tar_start;
+
+	while (1)
+	{
+		tar_header_t *header = (tar_header_t*)ptr;
+
+		if (header->filename[0] == '\0')
+		{
+			puts("[tar] EOF\n");
+			break;
+		}
+
+		unsigned int filesize = octal_to_int(header->size, 11);
+
+		if (strcmp(header->filename, filename) == 0)
+		{
+			printf("[tar] found file '%s', size=%u bytes\n", header->filename, filesize);
+
+			uint8_t *file_data = ptr+TAR_BLOCK_SIZE;
+			printf("[tar] content of '%s':\n", filename);
+			for (unsigned int i=0; i<filesize; i++)
+			{
+				putc(file_data[i]);
+			}
+			puts("\n");
+			return;
+		}
+
+		ptr += TAR_BLOCK_SIZE + ((filesize + TAR_BLOCK_SIZE-1) / TAR_BLOCK_SIZE) * TAR_BLOCK_SIZE;
+	}
+
+	printf("[tar] file '%s' not found\n", filename);
+}
+
+void ls_initrd(uint8_t* initrd)
+{
+	tar_header_t *header = (tar_header_t*)initrd;
+	
+	while (header->filename[0] != '\0')
+	{
+		printf("%s\n", header->filename);
+		uint32_t size = tar_parse_size(header->size);
+
+		uint32_t next_file_offset = ((size+TAR_BLOCK_SIZE-1)/TAR_BLOCK_SIZE)*TAR_BLOCK_SIZE;
+		header = (tar_header_t*)((uint8_t*)header + next_file_offset + TAR_BLOCK_SIZE);
+	}
+}
+
+void cat_initrd(uint8_t* initrd, const char* filename)
+{
+	tar_header_t *header = (tar_header_t*)initrd;
+
+	while (header->filename[0] != '\0')
+	{
+		if (strcmp(header->filename, filename) == 0)
+		{
+			uint32_t size = tar_parse_size(header->size);
+			uint8_t* file_content = (uint8_t*)header + 512;
+
+			for (uint32_t i=0; i<size; i++) putc(file_content[i]);
+			return;
+		}
+
+		uint32_t next_file_offset = ((tar_parse_size(header->size)+TAR_BLOCK_SIZE-1)/TAR_BLOCK_SIZE)*TAR_BLOCK_SIZE;
+		header = (tar_header_t*)((uint8_t*)header + next_file_offset + TAR_BLOCK_SIZE);
+	}
+
+	printf("File '%s' not found\n", filename);
+}