Added offset to elf_strings

the offset column in elf_strings lets us do a join with the
elf_dynamic_entries table for things like DT_NEEDED

README.md

@@ -282,6 +282,26 @@ For instance, the blow assumes the module name is `extension` from the
 ```
 </details>
 
+<details>
+<summary>Determine the NEEDED entries for a program</summary>
+
+_This may be improved in the future but for now there is a little knowledge of the
+polymorphic nature of the dynamic entries needed_.
+
+```console
+❯ sqlelf extension.cpython-311-x86_64-linux-gnu.so \
+> --sql "SELECT elf_strings.path, elf_strings.value
+FROM elf_dynamic_entries
+INNER JOIN elf_strings ON elf_dynamic_entries.value = elf_strings.offset
+WHERE elf_dynamic_entries.tag = 'NEEDED'"
+┌───────────────────────────────────────────┬───────────────┐
+│                   path                    │     value     │
+│ extension.cpython-311-x86_64-linux-gnu.so │ libcblas.so.3 │
+│ extension.cpython-311-x86_64-linux-gnu.so │ libc.so.6     │
+└───────────────────────────────────────────┴───────────────┘
+```
+</details>
+
 ## Development
 
 You may want to install the package in _editable mode_ as well to make development easier

sqlelf/elf.py

@@ -175,15 +175,38 @@ def strings_generator() -> Iterator[dict[str, Any]]:
                 # Python also treats the final null in the string by creating
                 # an empty item so we chop it off.
                 # https://stackoverflow.com/a/18970869
-                for string in str(strtab.content[1:-1], "utf-8").split("\x00"):
-                    yield {"path": binary_name, "section": strtab.name, "value": string}
+                strtab_name = strtab.name
+                for offset, string in split_with_index(
+                    str(strtab.content[1:-1], "utf-8"), "\x00"
+                ):
+                    yield {
+                        "path": binary_name,
+                        "section": strtab_name,
+                        "value": string,
+                        # we add one from the offset since we removed the
+                        # null byte at the start of the STRTAB
+                        "offset": offset + 1,
+                    }
 
     return Generator.make_generator(
-        ["path", "section", "value"],
+        ["path", "section", "value", "offset"],
         strings_generator,
     )
 
 
+def split_with_index(str: str, delimiter: str) -> list[tuple[int, str]]:
+    """Split a string with the delimiter and return the index
+    of the start of the split."""
+    start = 0
+    result = []
+    for i, c in enumerate(str):
+        if c == delimiter:
+            result.append((start, str[start:i]))
+            start = i + 1
+    result.append((start, str[start:]))
+    return result
+
+
 def make_symbols_generator(binaries: list[lief.Binary]) -> Generator:
     """Create the ELF symbols virtual table."""