first commit

.gitignore

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+/rootfs
+*.o
+.*.swp

Makefile

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+CFLAGS=  -Werror=discarded-qualifiers -Werror=ignored-qualifiers -Wfatal-errors -Wall -Wextra
+LDFLAGS= 
+OBJS=    main.o fs.o vfs.o init.o
+
+all: rootfs
+rootfs: $(OBJS)
+	$(CC) $^ -o $@ $(CFLAGS) $(LDFLAGS)
+%.o: %.c %.h
+	$(CC) -c $< $(CFLAGS)
+clean:
+	$(RM) *.o $(OBJS)

TODO

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+* shell
+* diagnostics
+* tests
+
+Example Output:
+_______________
+ls /: '/ /usr /home'
+ls /usr: '/usr/cp /usr/dd'

err.h

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+#pragma once
+
+typedef uint32_t err_t;
+enum{EOK=0,ENULL,};

fs.c

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+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+#include<time.h>
+#include"fs.h"
+#include"err.h"
+
+#define GENID() 0
+
+// Global filesystem for OS mounting
+FsHdr filesystem={0};
+
+err_t fs_mount_root(FsHdr*fs)
+{
+	if(!fs||fs->address==NULL)
+	{
+		printf("error: cannot mount NULL filesystem\n");
+		return ENULL;
+	}
+
+	filesystem=*fs;
+
+	return EOK;
+}
+
+static const char*fs_humanreadable(size_t val)
+{
+	static char buffer[1024]={0};
+	const char*append="?";
+	const char*const prefixes[]={"B","KiB","MiB","GiB","TiB"};
+
+	for(size_t i=0;i<sizeof(prefixes);++i)
+	{
+		if(val<1024)
+		{
+			append=prefixes[i];
+			break;
+		}
+		else
+			val/=1024;
+	}
+
+	sprintf(buffer,"%lu%s",val,append);
+
+	return (const char*)buffer;
+}
+
+void fs_print(const FsHdr*const fs)
+{
+	if(!fs)
+	{
+		printf("error: cannot print NULL fs\n");
+		return;
+	}
+
+	printf("id: %#08x\n",fs->id);
+	printf("address: %p\n",fs->address);
+	printf("length: %lu (%s)\n",fs->length,fs_humanreadable(fs->length));
+}
+
+err_t fs_pathto_inode(const char*const path)
+{
+	if(!path)
+		return ENULL;
+	return EOK;
+}
+
+err_t fs_stat(const char*const path)
+{
+	if(!path)
+		return ENULL;
+	return EOK;
+}

fs.h

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+/*****
+ *
+ * Interface for OS with
+ * filesystem modules
+ * fd table: connect file
+ * descriptors with actual
+ * files (inodes)
+ *
+ *****/
+
+#pragma once
+
+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+#include"err.h"
+
+#define BLOCKSIZE 4096
+#define VFS_GENID() 0
+
+typedef uint32_t fstype_t;
+
+// An inode represents an actual file
+typedef struct inode
+{
+	uint32_t atime;
+	uint8_t flags;
+} inode;
+
+// Filesystem header/super_block
+typedef struct FsHdr
+{
+	uint8_t*address;
+	size_t length;
+	uint32_t id;
+	fstype_t type;
+}FsHdr;
+
+extern FsHdr filesystem;
+
+// Function type to read from filesystem
+typedef void(*fs_read_t)(uint32_t offset,uint32_t size);
+typedef void(*fs_read_inode_t)(inode*inode_buffer,uint32_t offset);
+
+err_t fs_mount_root(FsHdr*fs);
+err_t fs_stat(const char*const path);
+void fs_print(const FsHdr*const fs);

init.c

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+/*****
+ *
+ * Mount rootfs filesystem for bootup
+ *
+ *****/
+
+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+#include"fs.h"
+#include"vfs.h"
+#include"init.h"
+#include"err.h"
+
+err_t init_mkrootfs(void)
+{
+	FsHdr fs=vfs_mkfs(128);
+	if(fs_mount_root(&fs)==ENULL)
+	{
+		printf("error: cannot mount NULL filesystem\n");
+		return ENULL;
+	}
+	return EOK;
+}
+
+void init_releasefs(void)
+{
+	vfs_free(&filesystem);
+}

init.h

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+#pragma once
+
+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+#include"fs.h"
+#include"err.h"
+#include"vfs.h"
+
+err_t init_mkrootfs(void);
+void init_releasefs(void);

main.c

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+/*****
+ *
+ * Simulate a filesystem
+ * not necessarily a shell
+ *
+ *****/
+
+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+#include"err.h"
+#include"fs.h"
+#include"vfs.h"
+#include"init.h"
+
+int main(void)
+{
+	if(init_mkrootfs()!=EOK)
+		printf("error: failed to initialize filesystem");
+
+	// allocate memory for virtual filesystem
+	// (VFS) and run commands to create inodes
+	// and then view their stats.
+
+	printf("mounted filesystem:\n");
+	fs_print(&filesystem);
+
+	init_releasefs();
+
+	printf("\nmounted filesystem:\n");
+	fs_print(&filesystem);
+}

result.h

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+#pragma once
+
+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+
+typedef struct Result
+{
+	bool success;
+	size_t size;
+	void*buffer;
+} Result;
+
+Result result_clone(void*buffer,size_t size)
+{
+	Result res={.success=false,.size=size,.buffer=buffer};
+}

vfs.c

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+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+#include<time.h>
+#include"fs.h"
+
+FsHdr vfs_mkfs(const size_t nblocks)
+{
+	const size_t length=BLOCKSIZE*nblocks;
+	const FsHdr fs={
+		.id=VFS_GENID(),
+		.length=length,
+		.address=malloc(length),
+	};
+	return fs;
+}
+
+void vfs_free(FsHdr*const fs)
+{
+	if(!fs)return;
+	if(fs->address)
+		free(fs->address);
+	fs->address=NULL;
+	fs->length=0;
+}

vfs.h

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+/*****
+ *
+ * Virtual filesystem for rootfs
+ *
+ *****/
+
+#pragma once
+
+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+#include"fs.h"
+
+#define VFS_FSTYPE 0x0001
+
+FsHdr vfs_mkfs(const size_t nblocks);
+void vfs_free(FsHdr*const fs);