diff --git a/tools/atree/files.cpp b/tools/atree/files.cpp
new file mode 100644
index 0000000..c675ab7
--- /dev/null
+++ b/tools/atree/files.cpp
@@ -0,0 +1,427 @@
+#include "files.h"
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <fnmatch.h>
+
+static bool
+is_comment_line(const char* p)
+{
+    while (*p && isspace(*p)) {
+        p++;
+    }
+    return *p == '#';
+}
+
+static string
+path_append(const string& base, const string& leaf)
+{
+    string full = base;
+    if (base.length() > 0 && leaf.length() > 0) {
+        full += '/';
+    }
+    full += leaf;
+    return full;
+}
+
+static bool
+is_whitespace_line(const char* p)
+{
+    while (*p) {
+        if (!isspace(*p)) {
+            return false;
+        }
+        p++;
+    }
+    return true;
+}
+
+static bool
+is_exclude_line(const char* p) {
+    while (*p) {
+        if (*p == '-') {
+            return true;
+        }
+        else if (isspace(*p)) {
+            p++;
+        }
+        else {
+            return false;
+        }
+    }
+    return false;
+}
+
+void
+split_line(const char* p, vector<string>* out)
+{
+    const char* q = p;
+    enum { WHITE, TEXT } state = WHITE;
+    while (*p) {
+        if (*p == '#') {
+            break;
+        }
+
+        switch (state)
+        {
+            case WHITE:
+                if (!isspace(*p)) {
+                    q = p;
+                    state = TEXT;
+                }
+                break;
+            case TEXT:
+                if (isspace(*p)) {
+                    if (q != p) {
+                        out->push_back(string(q, p-q));
+                    }
+                    state = WHITE;
+                }
+                break;
+        }
+        p++;
+    }
+    if (state == TEXT) {
+        out->push_back(string(q, p-q));
+    }
+}
+
+static void
+add_file(vector<FileRecord>* files, const string& listFile, int listLine,
+            const string& sourceName, const string& outName)
+{
+    FileRecord rec;
+    rec.listFile = listFile;
+    rec.listLine = listLine;
+    rec.sourceName = sourceName;
+    rec.outName = outName;
+    files->push_back(rec);
+}
+
+static string
+replace_variables(const string& input,
+                  const map<string, string>& variables,
+                  bool* error) {
+    if (variables.empty()) {
+        return input;
+    }
+
+    // Abort if the variable prefix is not found
+    if (input.find("${") == string::npos) {
+        return input;
+    }
+
+    string result = input;
+
+    // Note: rather than be fancy to detect recursive replacements,
+    // we simply iterate till a given threshold is met.
+
+    int retries = 1000;
+    bool did_replace;
+
+    do {
+        did_replace = false;
+        for (map<string, string>::const_iterator it = variables.begin();
+             it != variables.end(); ++it) {
+            string::size_type pos = 0;
+            while((pos = result.find(it->first, pos)) != string::npos) {
+                result = result.replace(pos, it->first.length(), it->second);
+                pos += it->second.length();
+                did_replace = true;
+            }
+        }
+        if (did_replace && --retries == 0) {
+            *error = true;
+            fprintf(stderr, "Recursive replacement detected during variables "
+                    "substitution. Full list of variables is: ");
+
+            for (map<string, string>::const_iterator it = variables.begin();
+                 it != variables.end(); ++it) {
+                fprintf(stderr, "  %s=%s\n",
+                        it->first.c_str(), it->second.c_str());
+            }
+
+            return result;
+        }
+    } while (did_replace);
+
+    return result;
+}
+
+int
+read_list_file(const string& filename,
+               const map<string, string>& variables,
+               vector<FileRecord>* files,
+               vector<string>* excludes)
+{
+    int err = 0;
+    FILE* f = NULL;
+    long size;
+    char* buf = NULL;
+    char *p, *q;
+    int i, lineCount;
+
+    f = fopen(filename.c_str(), "r");
+    if (f == NULL) {
+        fprintf(stderr, "Could not open list file (%s): %s\n",
+                    filename.c_str(), strerror(errno));
+        err = errno;
+        goto cleanup;
+    }
+
+    err = fseek(f, 0, SEEK_END);
+    if (err != 0) {
+        fprintf(stderr, "Could not seek to the end of file %s. (%s)\n",
+                    filename.c_str(), strerror(errno));
+        err = errno;
+        goto cleanup;
+    }
+    
+    size = ftell(f);
+
+    err = fseek(f, 0, SEEK_SET);
+    if (err != 0) {
+        fprintf(stderr, "Could not seek to the beginning of file %s. (%s)\n",
+                    filename.c_str(), strerror(errno));
+        err = errno;
+        goto cleanup;
+    }
+
+    buf = (char*)malloc(size+1);
+    if (buf == NULL) {
+        // (potentially large)
+        fprintf(stderr, "out of memory (%ld)\n", size);
+        err = ENOMEM;
+        goto cleanup;
+    }
+
+    if (1 != fread(buf, size, 1, f)) {
+        fprintf(stderr, "error reading file %s. (%s)\n",
+                    filename.c_str(), strerror(errno));
+        err = errno;
+        goto cleanup;
+    }
+
+    // split on lines
+    p = buf;
+    q = buf+size;
+    lineCount = 0;
+    while (p<q) {
+        if (*p == '\r' || *p == '\n') {
+            *p = '\0';
+            lineCount++;
+        }
+        p++;
+    }
+
+    // read lines
+    p = buf;
+    for (i=0; i<lineCount; i++) {
+        int len = strlen(p);
+        q = p + len + 1;
+        if (is_whitespace_line(p) || is_comment_line(p)) {
+            ;
+        }
+        else if (is_exclude_line(p)) {
+            while (*p != '-') p++;
+            p++;
+            excludes->push_back(string(p));
+        }
+        else {
+            vector<string> words;
+
+            split_line(p, &words);
+
+#if 0
+            printf("[ ");
+            for (size_t k=0; k<words.size(); k++) {
+                printf("'%s' ", words[k].c_str());
+            }
+            printf("]\n");
+#endif
+            
+            if (words.size() == 1) {
+                // pattern: DEST
+                bool error = false;
+                string w0 = replace_variables(words[0], variables, &error);
+                if (error) {
+                    err = 1;
+                    goto cleanup;
+                }
+                add_file(files, filename, i+1, w0, w0);
+            }
+            else if (words.size() == 2) {
+                // pattern: SRC DEST
+                bool error = false;
+                string w0, w1;
+                w0 = replace_variables(words[0], variables, &error);
+                if (!error) {
+                    w1 = replace_variables(words[1], variables, &error);
+                }
+                if (error) {
+                    err = 1;
+                    goto cleanup;
+                }
+                add_file(files, filename, i+1, w0, w1);
+            }
+            else {
+                fprintf(stderr, "%s:%d: bad format: %s\n", filename.c_str(),
+                        i+1, p);
+                err = 1;
+            }
+        }
+        p = q;
+    }
+
+cleanup:
+    if (buf != NULL) {
+        free(buf);
+    }
+    if (f != NULL) {
+        fclose(f);
+    }
+    return err;
+}
+
+
+int
+locate(FileRecord* rec, const vector<string>& search)
+{
+    int err;
+
+    for (vector<string>::const_iterator it=search.begin();
+                it!=search.end(); it++) {
+        string full = path_append(*it, rec->sourceName);
+        struct stat st;
+        err = stat(full.c_str(), &st);
+        if (err == 0) {
+            rec->sourceBase = *it;
+            rec->sourcePath = full;
+            rec->sourceMod = st.st_mtime;
+            rec->sourceIsDir = S_ISDIR(st.st_mode);
+            return 0;
+        }
+    }
+
+    fprintf(stderr, "%s:%d: couldn't locate source file: %s\n",
+                rec->listFile.c_str(), rec->listLine, rec->sourceName.c_str());
+    return 1;
+}
+
+void
+stat_out(const string& base, FileRecord* rec)
+{
+    rec->outPath = path_append(base, rec->outName);
+
+    int err;
+    struct stat st;
+    err = stat(rec->outPath.c_str(), &st);
+    if (err == 0) {
+        rec->outMod = st.st_mtime;
+        rec->outIsDir = S_ISDIR(st.st_mode);
+    } else {
+        rec->outMod = 0;
+        rec->outIsDir = false;
+    }
+}
+
+string
+dir_part(const string& filename)
+{
+    int pos = filename.rfind('/');
+    if (pos <= 0) {
+        return ".";
+    }
+    return filename.substr(0, pos);
+}
+
+static void
+add_more(const string& entry, bool isDir,
+         const FileRecord& rec, vector<FileRecord>*more)
+{
+    FileRecord r;
+    r.listFile = rec.listFile;
+    r.listLine = rec.listLine;
+    r.sourceName = path_append(rec.sourceName, entry);
+    r.sourcePath = path_append(rec.sourceBase, r.sourceName);
+    struct stat st;
+    int err = stat(r.sourcePath.c_str(), &st);
+    if (err == 0) {
+        r.sourceMod = st.st_mtime;
+    }
+    r.sourceIsDir = isDir;
+    r.outName = path_append(rec.outName, entry);
+    more->push_back(r);
+}
+
+static bool
+matches_excludes(const char* file, const vector<string>& excludes)
+{
+    for (vector<string>::const_iterator it=excludes.begin();
+            it!=excludes.end(); it++) {
+        if (0 == fnmatch(it->c_str(), file, FNM_PERIOD)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+static int
+list_dir(const string& path, const FileRecord& rec,
+                const vector<string>& excludes,
+                vector<FileRecord>* more)
+{
+    int err;
+
+    string full = path_append(rec.sourceBase, rec.sourceName);
+    full = path_append(full, path);
+
+    DIR *d = opendir(full.c_str());
+    if (d == NULL) {
+        return errno;
+    }
+
+    vector<string> dirs;
+
+    struct dirent *ent;
+    while (NULL != (ent = readdir(d))) {
+        if (0 == strcmp(".", ent->d_name)
+                || 0 == strcmp("..", ent->d_name)) {
+            continue;
+        }
+        if (matches_excludes(ent->d_name, excludes)) {
+            continue;
+        }
+        string entry = path_append(path, ent->d_name);
+#ifdef HAVE_DIRENT_D_TYPE
+		bool is_directory = (ent->d_type == DT_DIR);
+#else
+	    // If dirent.d_type is missing, then use stat instead
+		struct stat stat_buf;
+		stat(entry.c_str(), &stat_buf);
+		bool is_directory = S_ISDIR(stat_buf.st_mode);
+#endif
+        add_more(entry, is_directory, rec, more);
+        if (is_directory) {
+            dirs.push_back(entry);
+        }
+    }
+    closedir(d);
+
+    for (vector<string>::iterator it=dirs.begin(); it!=dirs.end(); it++) {
+        list_dir(*it, rec, excludes, more);
+    }
+
+    return 0;
+}
+
+int
+list_dir(const FileRecord& rec, const vector<string>& excludes,
+            vector<FileRecord>* files)
+{
+    return list_dir("", rec, excludes, files);
+}