[MOD/WIP] Start separating the main DB API

Not everything is available as of now, I'm still working on it, but it
builds and seems to work, and its 9PM, so that's worthapush.

src/Db/Flat.c

@@ -0,0 +1,274 @@
+#include <Db.h>
+
+#include <Memory.h>
+#include <Json.h>
+#include <Util.h>
+#include <Str.h>
+#include <Stream.h>
+#include <Log.h>
+
+#include <sys/types.h>
+#include <dirent.h>
+
+#include <pthread.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <errno.h>
+#include <string.h>
+
+#include "Db/Internal.h"
+
+typedef struct FlatDb {
+    Db base;
+    char *dir;
+    /* Theres not much to do here. */
+} FlatDb;
+typedef struct FlatDbRef {
+    DbRef base;
+
+    Stream *stream;
+    int fd;
+} FlatDbRef;
+
+static char
+DbSanitiseChar(char input)
+{
+    switch (input)
+    {
+        case '/':
+            return '_';
+        case '.':
+            return '-';
+    }
+    return input;
+}
+
+static char *
+DbDirName(FlatDb * db, Array * args, size_t strip)
+{
+    size_t i, j;
+    char *str = StrConcat(2, db->dir, "/");
+
+    for (i = 0; i < ArraySize(args) - strip; i++)
+    {
+        char *tmp;
+        char *sanitise = StrDuplicate(ArrayGet(args, i));
+        for (j = 0; j < strlen(sanitise); j++)
+        {
+            sanitise[j] = DbSanitiseChar(sanitise[j]);
+        }
+
+        tmp = StrConcat(3, str, sanitise, "/");
+
+        Free(str);
+        Free(sanitise);
+
+        str = tmp;
+    }
+
+    return str;
+}
+static char *
+DbFileName(FlatDb * db, Array * args)
+{
+    size_t i;
+    char *str = StrConcat(2, db->dir, "/");
+
+    for (i = 0; i < ArraySize(args); i++)
+    {
+        char *tmp;
+        char *arg = StrDuplicate(ArrayGet(args, i));
+        size_t j = 0;
+
+        /* Sanitize name to prevent directory traversal attacks */
+        while (arg[j])
+        {
+            arg[j] = DbSanitiseChar(arg[j]);
+            j++;
+        }
+
+        tmp = StrConcat(3, str, arg,
+                        (i < ArraySize(args) - 1) ? "/" : ".json");
+
+        Free(arg);
+        Free(str);
+
+        str = tmp;
+    }
+
+    return str;
+}
+
+static DbRef *
+FlatLock(Db *d, Array *dir)
+{
+    FlatDb *db = (FlatDb *) d;
+    FlatDbRef *ref = NULL;
+    size_t i;
+    char *path;
+    if (!d || !dir)
+    {
+        return NULL;
+    }
+
+    pthread_mutex_lock(&d->lock);
+    path = DbFileName(db, dir);
+    /* TODO: Caching */
+    {
+        int fd = open(path, O_RDWR);
+        Stream *stream;
+        struct flock lock;
+        if (fd == -1)
+        {
+            ref = NULL;
+            goto end;
+        }
+
+        stream = StreamFd(fd);
+        
+        lock.l_start = 0;
+        lock.l_len = 0;
+        lock.l_type = F_WRLCK;
+        lock.l_whence = SEEK_SET;
+
+        if (fcntl(fd, F_SETLK, &lock) < 0)
+        {
+            StreamClose(stream);
+            ref = NULL;
+            goto end;
+        }
+
+        ref = Malloc(sizeof(*ref));
+        DbRefInit(d, &(ref->base));
+        ref->fd = fd;
+        ref->stream = stream;
+        ref->base.ts = UtilLastModified(path);
+        ref->base.json = JsonDecode(stream);
+        if (!ref->base.json)
+        {
+            Free(ref);
+            StreamClose(stream);
+            ref = NULL;
+            goto end;
+        }
+        
+        
+        ref->base.name = ArrayCreate();
+        for (i = 0; i < ArraySize(dir); i++)
+        {
+            ArrayAdd(
+                ref->base.name, 
+                StrDuplicate(ArrayGet(dir, i))
+            );
+        }
+    }
+end:
+    Free(path);
+    if (!ref)
+    {
+        pthread_mutex_unlock(&d->lock);
+    }
+    return (DbRef *) ref;
+}
+
+static bool
+FlatUnlock(Db *d, DbRef *r)
+{
+    FlatDbRef *ref = (FlatDbRef *) r;
+
+    if (!d || !r)
+    {
+        return false;
+    }
+
+    lseek(ref->fd, 0L, SEEK_SET);
+    if (ftruncate(ref->fd, 0) < 0)
+    {
+        pthread_mutex_unlock(&d->lock);
+        Log(LOG_ERR, "Failed to truncate file on disk.");
+        Log(LOG_ERR, "Error on fd %d: %s", ref->fd, strerror(errno));
+        return false;
+    }
+
+    JsonEncode(ref->base.json, ref->stream, JSON_DEFAULT);
+    StreamClose(ref->stream);
+
+    JsonFree(ref->base.json);
+    StringArrayFree(ref->base.name);
+    Free(ref);
+
+    pthread_mutex_unlock(&d->lock);
+    return true;
+}
+static DbRef *
+FlatCreate(Db *d, Array *dir)
+{
+    FlatDb *db = (FlatDb *) d;
+    char *path, *dirPath;
+    Stream *fp;
+    DbRef *ret;
+
+    if (!d || !dir)
+    {
+        return NULL;
+    }
+    pthread_mutex_lock(&d->lock);
+
+    path = DbFileName(db, dir);
+    if (UtilLastModified(path))
+    {
+        Free(path);
+        pthread_mutex_unlock(&d->lock);
+        return NULL;
+    }
+
+    dirPath = DbDirName(db, dir, 1);
+    if (UtilMkdir(dirPath, 0750) < 0)
+    {
+        Free(path);
+        Free(dirPath);
+        pthread_mutex_unlock(&d->lock);
+        return NULL;
+    }
+    Free(dirPath);
+
+    fp = StreamOpen(path, "w");
+    Free(path);
+    if (!fp)
+    {
+        pthread_mutex_unlock(&d->lock);
+        return NULL;
+    }
+
+    StreamPuts(fp, "{}");
+    StreamClose(fp);
+
+    /* FlatLock() will lock again for us */
+    pthread_mutex_unlock(&d->lock);
+
+    ret = FlatLock(d, dir);
+
+    return ret;
+}
+
+Db *
+DbOpen(char *dir, size_t cache)
+{
+    FlatDb *db;
+    if (!dir)
+    {
+        return NULL;
+    }
+    db = Malloc(sizeof(*db));
+    DbInit(&(db->base));
+    db->dir = dir;
+    db->base.cacheSize = cache;
+
+    db->base.lockFunc = FlatLock;
+    db->base.unlock = FlatUnlock;
+    db->base.create = FlatCreate;
+    db->base.close = NULL;
+
+    return (Db *) db;
+}