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Encode action labels as UTF-8 #13

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Encode action labels as UTF-8 #13

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23 changes: 17 additions & 6 deletions header-gen/src/main.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -55,10 +55,21 @@ const ACTION_HEADER_SIZES = {
* @returns The binary blob as an ArrayBuffer.
*/
export function generateBlob(data: MlModelHeader): ArrayBuffer {
// Labels are stored as UTF-8, so encode them first and use byte lengths throughout
const encoder = new TextEncoder();
const actions = data.actions.map(action => {
const labelBytes = encoder.encode(action.label);
// label_length is a uint8_t and includes the null terminator
if (labelBytes.length + 1 > 255) {
throw new Error(`Action label longer than 254 bytes when UTF-8 encoded: "${action.label}"`);
}
return { ...action, labelBytes };
});

// Calculate size of the actions and labels within, including null terminators and padding
const fixedActionSize = Object.values(ACTION_HEADER_SIZES).reduce((acc, size) => acc + size, 0);
let actionsSize = data.actions.reduce((acc, action) => {
const actionStructSize = fixedActionSize + action.label.length;
let actionsSize = actions.reduce((acc, action) => {
const actionStructSize = fixedActionSize + action.labelBytes.length;
// Each action struct is padded at the end to align to 4 bytes
const structPadding = (actionStructSize % 4 === 0) ? 0 : 4 - (actionStructSize % 4);
return acc + actionStructSize + structPadding;
Expand Down Expand Up @@ -86,13 +97,13 @@ export function generateBlob(data: MlModelHeader): ArrayBuffer {
offset = addToView(view, offset, data.actions.length, CONST_SIZES.number_of_actions);

// Add action structures
data.actions.forEach(action => {
actions.forEach(action => {
const start_offset = offset;
view.setFloat32(offset, action.threshold, true);
offset += ACTION_HEADER_SIZES.threshold;
offset = addToView(view, offset, action.label.length + 1, ACTION_HEADER_SIZES.label_length);
for (let i = 0; i < action.label.length; i++) {
offset = addToView(view, offset, action.label.charCodeAt(i), 1);
offset = addToView(view, offset, action.labelBytes.length + 1, ACTION_HEADER_SIZES.label_length);
for (const byte of action.labelBytes) {
offset = addToView(view, offset, byte, 1);
}
offset = addToView(view, offset, 0, 1); // null terminator
// Align to 4 bytes and pad with zeros
Expand Down
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